cancel menu refactoring: it should be usable from external plugins
Merge branch 'master' into beta

Conflicts:
	src/org/geometerplus/android/fbreader/ShowCancelMenuAction.java
	src/org/geometerplus/android/fbreader/preferences/PreferenceActivity.java
	src/org/geometerplus/fbreader/fbreader/FBReaderApp.java