Migrate event associations for bookings
Migrate booking list for event
Allow multiple locator targets in url_for()

Also allow RHs with parameterless __init__ methods (req is unused anyway)
Migrate booking details for event
Don't use UHs for the migrates RHs
Migrate booking modification for event
Remove debug crap
Migrate booking cloning for event
Don't allow room selection when cloning

This is pretty much a temporary solution until we preserve the form data
when changing the room via the dropdown selector.
Rename event_reservations.py -> event.py

Otherwise room details wouldn't fit in there
Migrate room details for event
Use correct details link in mini details widget
Migrate simple room booking for event
Set can_override in 3-step booking process
Migrate room booking for event
Fix back links in 3-step process for event
Disable "existing bookings" tab if there are none
Log cancellation reason if one is provided
Fix booking list retrieval and event deletion

They were still accessing old RB code
On event deletion associated bookings are now cancelled instead of beign
deleted.
Remove apparently-unused ConferenceListUsedRooms