ConsoleActivity: Menu optimizations and bugfix

- refactor redundant code in onCreateOptionsMenu and onPrepareOptionsMenu:
  onCreateOptionsMenu did the same enabling/disabling of the buttons
  that onPreareOptionsMenu was doing all the time, anyways.
  It is not needed, and was removed.

- Disable the sym/ctrl/key/... buttons, too, in case no session is open.

- Work around a bug in android that does not properly call onPrepareOptionsMenu
  in case the device has a hard menu button and the menu button is pressed
  for the first time.
  This could lead to an invalid menu, like buttons being enabled, when they
  actually shouldn't be, because we got disconnected in the meantime.
  This is related to the ActionBar and thus happens only on API13+.
  Compare
  * http://code.google.com/p/android/issues/detail?id=24231
  * http://stackoverflow.com/questions/12405825/how-can-i-force-the-onprepareoptionsmenu-method-to-fire
  * http://stackoverflow.com/questions/12886751/jelly-bean-not-calling-onprepareoptionsmenu-when-opening-the-menu-for-the-firs
  The invalidateOptionsMenu() solution is pretty bad, because it causes the whole menu to be rebuilt.
  Instead, just use onMenuOpened(), this is triggered correctly and has the same effect.