[FIX] RoomBooking calendar: protected rooms

* Users not having rights to book a protected room get a popup preventing it.
* closes #1247
[IMP] jQuery dialogs for conflicting bookings
[FIX] Fixed group check workflow

 * We should not assume a room is OK just because it is not protected (there can be booking collisions);
 * Fixed error in case room is not publicly bookable but has no booking group;
 * Also simplified collision checking code;
[VER] Revert part of 9da502ad90c

 * Causes regression in previously working code
[VER] Reverted part of 93eff750
[FIX] requests auth object - do not reuse

 * This was breaking the authentication process, was it was shared using a singleton;
[FIX] CSS attribute mistake
[FIX] Removing element while iterating list

 * Thanks to Juan Cabrera for the patch;
Merge branch 'v1.1'
[FIX] Migration - warning in case of unknown task

 * Not exception