Removed unused icons, replaced others with their material equivalents. Updated both the regular and debug app icons, including properly-sized versions for each DPI bucket. Added new notification icon.
Merge remote-tracking branch 'upstream/android-l-update' into android-l-update

Conflicts:
	android/build.gradle
Fixes #298. Removed useless notification setting.
Merge branch 'android-l-update' into broadcast_message

Conflicts:
	android/src/main/java/com/thebluealliance/androidclient/gcm/notifications/GenericNotification.java