Enhanced Playlist Scheduling
Currently, a playlist can be scheduled or not.
If scheduled, a schedule has to be set based on both date AND time windows.
There may however be cases where you may (well...this is true in our case) want to schedule a playlist to run/be activate between:
* Certain times ONLY (ie no date constraint) - eg 06:00 - 18:00 for daytime jungles
* Certain dates only (ie no time constraints) - eg all day between 01 May - 31 Aug for "summer" jingles