Add receivers for broadcast intents.

Hi.

I wonder if you might consider incorporating the attached.

It implements three broadcast receivers for CC:

- `com.jadn.cc.services.external.PAUSE` (pause playback)
- `com.jadn.cc.services.external.PLAY` (begin playback)
- `com.jadn.cc.services.external.PAUSEPLAY` (toggle play/pause)

Why?  Because these let me control CC from Tasker (or any similar automation app).

For example, I can have CC begin playback automatically when headphones are inserted, but -- in my case -- only in the morning.  I use a different audio app in the evening.

I'm not too familiar with Android intent handling, so there may be a better way to achieve the same thing.  But, at least this doesn't seem to break anything.

Thanks!

Steve (long-time CC-pro user).