Added boolean attribute "show_entry_tour" to User instances. It defaults to true.

This flag will indicate whether to show the user a tour when he opens an entry for the first time.
Added support to updating the show_entry_tour flag for a user.
Added controller support to updating the show_entry_tour flag for the current user.
WIP: show a tour when the user opens an entry for the first time.
WIP: show a tour when the user opens an entry for the first time.