fixed possible exception
cleanup
Merge branch 'master' into beta

Conflicts:
	src/org/geometerplus/android/fbreader/preferences/PreferenceActivity.java
fixed #122: start/stop screen wakelock in onWindowFocusChanged (not in onResume/onPause)
Merge branch 'master' into beta

Conflicts:
	src/org/geometerplus/android/fbreader/FBReader.java