ods: added source id to OdsSource
ods: allowed regular gcm msgs mixed with debug flag
ods: use source id instead of classname in GcmUtils
Added MainPreferencesActivity for managing ods server name
Suppress deprecation warning in MainPreferencesActivity

... for now. Sooner or later a switch from activities to
fragments will be required.
ods: fixed typo
ods: GcmBroadcastReceiver triggers sync on msg receive