[Android] Decouple Dolphin.ini config file saving from GameListActivity. It doesn't make sense to save the config AFTER control is returned from PrefsFragment to GameListActivity, since the main purpose of PrefsFragment is to handle the user settings. So, instead, we call SaveConfigToDolphinIni() in the PrefsFragment.onDestroy() method. This way, when the PrefsFragment object is being 'destroyed', it will write the settings to the ini.