Refector: clean up code.
Display note count on network graph.
Fix RoutingError when changing username to non ascii char.
New issue button was not follows to external tracker if it is selected. fixed #3386
use convenient method to check for empty project repo
Fixed UsersProject.in_projects

I discovered while trying to use UserTeam#remove_member() that
UsersProject.in_projects was broken.  So I wrote test cases to test what
I was trying to do and fixed the underlying problem.
use NotificationService for handle notify logic when MR created
Use notificationService for MR reassigned
Move new_note email logic to NotificationService
refactor observers. Added BaseObserver with helper methods
refactor observers test since email logic moved to service
Settings replaced by Gitlab.config
stub notification in event model
Merge pull request #3407 from NARKOZ/patch-1

use convenient method to check for empty project repo
Link to accepting issues on feedback forum.
annotated
notification scaffold
Prepare UI for notification settings
NotificationService respects disabled notifications now
Fix NotificationService NameError for new issue