Add roles as nested routes to track (for the track organizer role)
Allow transition from to_accept to to_reject and backwards
Split Track#valid_dates validation to many independent ones
Show all the confirmed tracks in the conference's splashpage
Add comment in admin/Tracks#toggle_cfp_inclusion
Rewrite admin/TracksController#accept spec
Add feature spec for track requests
Change 'In' to 'Room' in Tracks#index
Rewrite Track#overlapping
Refactor code in ProposalsController
Fix typos
Also, the part of the schedule event is deleted and the length of the event types
changes to the nearest suitable after changing the length of the interval.
This closes#1220