implement collection add/delete methods

[JonnyJD]

The type of a collection was implemented in #170 and we can work with collections of releases.
After the implementation for events is complete (#168) we should also implement handling of collections of events. (blocked by #168)

There are some comments about this in #170.

[alastair]

Ian also implemented get works, and it's live on beta. No work submission though. Is there a event submit api yet?

[JonnyJD]

No clue actually. I don't follow server development closely ATM.

[alastair]

This is waiting on http://tickets.musicbrainz.org/browse/MBS-8652 and http://tickets.musicbrainz.org/browse/MBS-8651

[mineo]

Both upstream tickets have been fixed.

[fin0]

Any chance that this is implemented soon (I need it for works :) )?

[mineo]

Unfortunately I think none of the usual suspects is going to implement this in the near future :( If you feel like implementing it on your own, you can probably just copy&paste https://github.com/alastair/python-musicbrainzngs/blob/master/musicbrainzngs/musicbrainz.py#L1324-L1337 and replace releases with the names of the entity types that can be put into collections.

[fin0]

Worked out fine, thank you very much! :)

[mineo]

@fin0 Would you mind submitting a pull request for those changes?