Ability to move issue to another project
Tasks:
- [x] Create scaffold of service that will move issue to another project.
- [x] Close old issue, add system note about moving issue to a new project.
- [x] Create a new issue, add system note about issue being moved from old project.
- [x] Check if issue can be moved to another project before executing service
- [x] Check permissions when moving an issue (`:admin_issue` ability)
- [x] Display select box for a new project when editing an issue
- [x] Show only projects that issue can be moved into in that select box
- [x] Add project select handler, helper and some permission filters to it
- [x] Preserve as much information as possible, including author
- [x] Prepare mechanisms that unfolds local references in issue description
- [x] Rewrite issue description with references unfolding and add some specs for it
- [x] Rewrite all system notes and comments attached to issue that is being moved
- [x] Update `Label` so that is was able to create cross reference labels (separate MR)
- [x] Add notifications about moving issue to another project
- [x] Display confirmation alert/message when issue move has been requested
- [x] Make it possible to undo selecting project where issue will be moved to
- [x] Add column to issue, that will indicate if it has been moved to another project
- [x] Do not allow to move issue that has been already moved
- [x] Write top-to-bottom feature spec in RSpec instead of Spinach
UI:


Closes#3024
See merge request !2831
Changing filter dropdowns shows loading
Instead of doing a full refresh of the page - i've modified the filterResults method on the Issues object to work for this form as well

Closes#14359
See merge request !3237
External Users
The user has the rights of a public user execpt it can never create a project, group, or team. Also it cant view internal projects.
Partially fix for both #4009 and #13938 (except the LDAP sync or a pattern to detect external users)

See merge request !3171
Added discard button to comment form
Also changed the labels on the buttons to better match the action they are completing.
Closes#8057
See merge request !3085
Improve performance of getting issues on group level
For testing I used the URL http://localhost:3000/groups/gitlab-org/issues?milestone_title=8.1. Prior to these changes said URL would take about 10-12 seconds to load. By applying these changes the loading time has been reduced to roughly 2-3 seconds.
There's still some stuff going on in some views that I have to look at, resolving those changes might reduce the loading time a bit more. I also still have to check if I didn't break too many tests.
Fixes: gitlab-org/gitlab-ce#3707 gitlab-org/gitlab-ce#4071
See merge request !2318
Adds settings menu to the top for editting and leaving projects
@creamzy @skyruler @dzaporozhets
Menu contents depends on user's rights.
Fixes#4221




See merge request !2195
Fix method that ensures authentication token
Until now, `ensure_#{token_filed_name}!` method didn't persist new token in database.
This closes#4235.
See merge request !2185
Make CI Lint form synchronous
This removes `remote: true` from CI Lint form, making it synchronous
form. This also removes some complexity related to displaying lint
messages.
View also has been updated, removed deprecated Bootstrap 2 tags.
Improved design.
See merge request !2171
This removes `remote: true` from CI Lint form, making it synchronous
form. This also removes some complexity related to displaying lint
messages.
View also has been updated, removed deprecated Bootstrap 2 tags.
Improved design.
Closes#4206