Use BaseActivity.this as the client for volume callbacks.

Without this it registers as the sub-class, and is not removed correctly
when the activity is paused.
Add "changedSong" to the conditions that trigger onPlayerStateReceived.

Without this the displayed songs in PlayerListActivity don't update.
Fix two NPEs when no players are connected to the server.

(cherry picked from commit 0c167b3285670fc385cd00cef933bf3416936e0e)
Update to the latest version of dependant libraries and tools.

SDK version stays at 19 to avoid bringing in Wear / Material Design themes
which are not handled well.
Prepare for release 1.2.0-beta-1.
Use equals() instead of == when comparing songs.

Fixes bug where the song was always considered to be different.

(cherry picked from commit d5318de40a9165bd20baf80e97888dae7933b659)
Fix a bug where the UI was not updating when returning to some activities.

It was possible to get in to a situation where the service binding had
happened and the handshake had not completed. Attempts to e.g. fetch
album artwork URLs, or order information from the server in this period
would fail. This manifested as e.g. returning to SongListActivity from
another application and the album artwork and track details disappearing.

Fix by:

- Adding a HandshakeNotCompleteException to the service, thrown by methods
  that require the handshake to have completed.

- Changing ItemListActivity to request pages ordered before the handshake
  completes, not just before the service binding completes.

- Changing NowPlayingFragment and SongListActivity to update the UI after
  the handshake completes.

Fixes https://code.google.com/p/android-squeezer/issues/detail?id=79.
Update to Gradle 2.2.1.
Prepare for release 1.2.0-beta-2.
Merge branch 'develop' into eventbus

* develop:
  Prepare for release 1.2.0-beta-2.
  Update to Gradle 2.2.1.
  Fix a bug where the UI was not updating when returning to some activities.
  Use equals() instead of == when comparing songs.
  Prepare for release 1.2.0-beta-1.
  Update to the latest version of dependant libraries and tools.
  Fix two NPEs when no players are connected to the server.
  Add "changedSong" to the conditions that trigger onPlayerStateReceived.
  Use BaseActivity.this as the client for volume callbacks.

Conflicts:
	Squeezer/src/main/java/uk/org/ngo/squeezer/NowPlayingFragment.java
	Squeezer/src/main/java/uk/org/ngo/squeezer/framework/BaseActivity.java
	Squeezer/src/main/java/uk/org/ngo/squeezer/service/SqueezeService.java