Don't recreate Reader or Notificaion VSs if already displayed.  Refs #112.

Check to see if the current detailViewController is the same class as the menu item the user tapped.
If so, don't recreate it, just close the sidebar.
Fixes #112. Reuse the same background context instead of creating a new one everytime we sync.
Removing "Sign out" button from add blogs screen. Fixes #244
Merge branch 'develop' into feature/feedback