This commits also fixes two minor issues:
- Ensure notes that the current user is not allowed to see are not
returned in the AJAX notes loading
- Ensure the notes counter badge is decremented of 1 instead of 2
Automatically fork a project when not allowed to edit a file.
Fixes#3215.
To do:
- [ ] Add tests
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## "Edit" button on file in a project the user does NOT have write access to

## Clicking will automatically create a fork

## When the fork has been created, the user is returned to the edit page on the original project with a notice

## The user cannot change the target branch and is informed that editing will start an MR

## Hitting "Commit changes" will commit and start an MR from my fork to the origin project

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## "Create file, "Upload file" and "New directory" buttons in a project the user does NOT have write access to

## Clicking any of these options will automatically create a fork

## When the fork has been created, the user is returned to the tree page on the original project with a notice

## Clicking "New directory" again will show the modal. The user cannot change the target branch and is informed that editing will start an MR

## Hitting "Create directory" will commit and start an MR from my fork to the origin project

cc @dzaporozhets @skyruler
See merge request !2145