Added two new configuration options for specifying a signoff video to the per-station configurations:

#used at sign-off time (played once)
'sign_off_video': "catalog/anthem_signoff.mp4",
#used when the channel is offair 
'off_air_video': "catalog/off_air_pattern.mp4",

and then an option in the schedule configuration to note when to run it - the following will cause sign-off at 3am:

3: {'event' : 'signoff'} 

About Sign Off events

A signoff event is specified by assigning a time slot to {'event' : 'signoff'} and will cause the video file specified by sign_off_video to be played once at the top of the hour. If off_air_video is specified, then the remainder of the hour will be filled by looping off_air_video.

About Off Air time
If a time slot is not specified, it will be considered as off-air for schedule creation. If off_air_video is specified, then the slot will be filled by looping off_air_video.