Returns schedules for a defined set of channels over a requested period.
Schedules are requested in hour blocks and returned grouped by the channel they belong to.
For example, to load 12 hours of schedules for channels 4343 and 5234,
on 21/2/2017 starting from 08:00.
Please remember that date and hour combined represent a normal datetime,
so they should be converted to UTC on the client - this will help to avoid
issues with EPG schedules near midnight.
If a channel id is passed which doesn't exist then this endpoint will return an empty schedule list for it. If instead we returned 404, this would invalidate all other channel schedules in the same request which would be unfriendly for clients presenting these channel schedules.