feat(notifications): display notification when user is mentioned

when user is mentioned there will be an unread notification in the list

SD-684 SD-656
fix(views): hide attach to desk btn on edit/my content

you can't change the desk because you only see the view on the desk it was defined.
and if there is no desk it doesn't make sense too..

SD-546
feat(tasks): Listing current user's tasks in workspace.

SD-72
fix(users): extend userList service

and make use of it in mentions
feat(preferences): user prefrences ui
fix(notifications): add styling to notification label
fix(checkbox): Reverted checkboxes to native ones.

SD-688
fix(authoring): update styling for widgets
Merge remote-tracking branch 'ozan/checkbox-fix' into devel
Merge remote-tracking branch 'nikola/devel' into devel
fix(mentions): remove predicting the content

because of badly positioned elements
Merge remote-tracking branch 'upstream/devel' into devel