Etar: Support Go devices without widgets permission

 * Add widget safeguards against unsupported widgets
 * Validate the feature support only once to avoid recurrence

 * Based upon the following commit from packages/apps/Email:
   Commit: AOSP/Email - Added WidgetService#isWidgetSupported
           to check if widgets are supported on the device and
           avoid calling AppWidgetManager#getInstance if not
           supported to avoid NullPointerException.
   Change-Id: I9fff575684e935a96ffe3e3d732a854b9cec461c

Signed-off-by: Adrian DC <radian.dc@gmail.com>
Change-Id: I1d5f6dfc70f6549b98cf156e3039629d75b9d1cd