Use gradle 2.1, and version 0.14.0 of the Gradle plugin.
Move volume key handling in to BaseActivity.
Merge branch 'volume-panel' into develop

Conflicts:
	Squeezer/src/main/java/uk/org/ngo/squeezer/framework/BaseActivity.java
	Squeezer/src/main/java/uk/org/ngo/squeezer/itemlist/PlayerListActivity.java