Create preference to watchlist pages after rollbacking

This change adds a  preference in the 'watchlist' section to
automatically watchlist a page after rollbacking.

The setting is only visible, if the user has the 'rollback'-right.
I have removed the watch reverts function per advice by Vogone.

Bug: 4488
Change-Id: I3aa831c9c04d627684641af0ca5a332795c87062