add shared repository support

Fix issue close and reopen button text and styles

Small fixes for editing files

Refactor tree views and improve consistency

Remove redundant branch labels from MR form

Fixes #1525

Small Note code cleanup

Fix link to wiki page in wiki comment notification

Improve development experience.

Fix notification for notes on a wall. (regression)

The fact that Notes on Walls have a noteable_type value of "nil" got
lost in the refactoring of the observer.