register receiver @ activity's onStart instead of onServiceConnected
Added basic gogoc settings to shared preferences (not used yet by app)
Simplified enable/disable logic for userid/passwd entries by using
Preference.OnPreferenceChangeListener instead of the overhead of
registering/unregistering a SharedPreferences.OnSharedPreferenceChangeListener
Main activity UI enhancements

* Display the window after connected with servie
* Move UI setup to onContentChange method
* Fix crash if attempting to open menu before being connected to service