Add "canceled" attribute to Broadcast
To manage correct EpisodeIdentifiers and to have a qick way for remove shows from the schedule, we may add an canceled attribute. Broadcast having this set True are
- Not counted for EpisodeIdentifiers who are binded on the number of on air Broadcast premieres
- Are not shown or visualized differently in some frontends
- Are not able to have a linked episode and some other stuff we have to check.