Open existing reservation details in new tab

When viewing the calendar widget during the booking process
Partial revert of 91db4ff2
Keep parameters when cloning bookings
Small style fixes
Install dev requirements in environment
Merge branch 'v1.2'
Merge branch 'master' into wip/future-db
i18n-related encoding fixes

Fixed double decodings and encodings. Added unicode-safety to _().
Typo in migration_to_sqlalchemy
Add Room.set_attribute_value

Also:
* Add __repr__ for RoomAttributeAssociation
* Rename Room.update_name
Rename Location.getAttributeByName()
Migrate Holiday

* New table holidays
* Holidays stored per location
* Add Alembic revision
* Remove old HolidaysHolder
Update FoundationSync call
Fix room_occupation script
Rename script to room_occupancy
Fix available rooms filter
Remove unused imports
Add qtip on disabled booking buttons
Highlight conflict checkboxes in booking pages
Fix long room/location names in roomselector