Limit access to projects based on the user rights and add per project rooms

The calendar now respects the user roles and permissions and only shows the projects
the user has access to.
Be aware, that now each user that wants to create, update and delete bookings has
to have these rights for the project! (Administration->Roles and permissions).

Signed-off-by: Tobias Droste <tdroste@gmx.de>
Merge branch 'master' of https://github.com/dro123/redmine_meeting_room_calendar