Added blank state to issues
## What does this MR do?
Adds new blank state to issues when no issues exist.
Part of #18519
## Screenshots (if relevant)

See merge request !4908
New diff notes
Fixes#12732, #14731, #19375, #14783
Builds on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4110
To do:
- [x] Get it mostly working
- [x] Validate position validity
- [x] Fix: Don’t link to `#`
- [x] Fix: Base ref can be `nil`, potentially, when the MR has an oprhan source branch => Yep, doesn’t work. We need to store a `start_id`
- [x] Optimize: Fewer duplicate `git diff` compares
- [x] Optimize: Pass paths to `PositionTracer#diff` for faster diffs
- [x] Refactor: Use `head_id` in `MergeRequest`/`MergeRequestDiff` instead of `source_sha`
- [x] Refactor: Convert existing array-based diff refs to the DiffRefs model
- [x] Tweak: Use `note_type` in `Autosave` key
- [x] Tweak: Remove `line_code: note.line_code` from `link_to_reply_discussion`
- [x] Update: `SentNotifications` and reply-by-email receiver
- [x] Update: MR diff notification email
- [x] Update: API (MR, Commit note creation and entity)
- [x] Update: GitHub importer
- [x] Address any other TODO comments
- [x] Fix: Suppress "edited 4 minutes ago"
- [x] Write tests
- [x] `LineMapper`
- [x] `PositionTracer`
- [x] `Position`
- [x] `DiffPositionUpdateService`
- [x] `DiffNote`
- [x] `MergeRequests::RefreshService` / `MergeRequest#update_diff_notes_positions`
- [x] Make sure commits with diff notes don't get cleaned up, since this would prevent the diff notes from being rendered (https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5062)
Future improvements:
- Display unresolved comments on files outside the diff, if the comment was added when that file _was_ part of the diff
- Allow commenting on sections between hunks, when expanding the diff using `...`
- (We'd need to generate line code based on Position if we have it, even if it falls outside bounds of diff)
- `diff_hunk` on diff note API entity
- Show diff hunk in notification email
- Resolved line notes would have a boolean, and be inactive through `notes.any? { !active? || resolved? }`
- Multi line notes would store a number of positions, and do the right thing (™) in grouping and then rendering if the first item is multiline? => true
- Image diff notes could store x,y,width,height instead of old_line,new_line for similar grouping. Does it need a reference to say if it's on old or new? These can't have line_codes, clearly. Rendering would be interesting.
- Show commit line comments in the MR diff
- Comment on specific selected words
- Comment on file header
- Unfold top of discussion diff note
- New diff notes API for commits and MRs
/cc @rspeicher
See merge request !4101
Added 100% width to open dropdown menus on mobile
## What does this MR do?
Sets dropdown-menus to be 100% width on small screens.
## Are there points in the code the reviewer needs to double check?
Do we want this on all dropdown menus or only dropdown menus activated by full-width buttons?
/cc @dzaporozhets
## Why was this MR needed?
Mobile UX.
## What are the relevant issue numbers?
Closes#18858.
## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?
- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
- [ ] Added for this feature/bug
- [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)
See merge request !4844
Added user avatar to header
## What does this MR do?
Adds the users avatar to the header with a dropdown for profile & sign out.
## What are the relevant issue numbers?
Closes#18543
## Screenshots (if relevant)


See merge request !4939
Align flash messages with left side of page content
## What does this MR do?
- align flash messages with left side of page content
## Are there points in the code the reviewer needs to double check?
- flash messages in general
## Why was this MR needed?
- flash messages didn't fit new design
## What are the relevant issue numbers?
closes #18688
## Screenshots
# Before

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# After

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The left padding will be fixed by !4854

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See merge request !4959
Adds focus state style to markdown area buttons.
## What does this MR do?
It makes it possible to see when the button is focused when tabbing through the interface. This is for the new markdown buttons in the comment field.
See merge request !4867
Implement UI for new project page
## What does this MR do?
Updates the project creation page to conform with the latest UI updates.
## Are there points in the code the reviewer needs to double check?
Ney.
## Why was this MR needed?
Updated UI.
## What are the relevant issue numbers?
Closes#2542.
## Screenshots (if relevant)
**Desktop:**

**Mobile:**

See merge request !4766
Completed new project page
Updated CHANGELOG
Corrected 'Create project' button
Made responsive
Added gitlab export button
Changed Spinach test to match updated UI
reverted test changes and fixed UI
Corrected 'Repo by URL' text
Fixed static namespace style
Added errors partial
Added padding to bottom of page-with-sidebar
Hide nav arrows by default
## What does this MR do?
- Fixes the arrow icon flashing on page load
- Removes settings dropdown at higher breakpoint
- Removes unneeded CSS
Closes#18941
## Screenshots (if relevant)
Arrow flashing bug:

Settings dropdown breaking nav:
<img src="/uploads/4351035f4cf8cb9fd892b621e6339e50/Screen_Shot_2016-06-21_at_4.25.50_PM.png" width="800px">
@alfredo1 would you mind double checking this to make sure the arrow flashing is definitely not happening?
See merge request !4843
Fixed issue with navbar counts being misaligned
## What does this MR do?
Fixes an issue in FireFox with the number counts being mis-aligned.
## What are the relevant issue numbers?
Closes#18916
## Screenshots (if relevant)

See merge request !4829
Fixed hover of date picker calendar
## What does this MR do?
Fixes the hover styling of days on the datepicker dropdown in the issuable sidebar.
## Screenshots (if relevant)

See merge request !4786