gmoccapy_1_1_5_1 - solved bug not resetting the gmoccapy error pin

ver 1.1.5.1
- solved a bug related to the gmoccapy error pin. This pin has not been reseted
  if the user used the mouse or touch screen and errased the message by clicking
  the message button. It was only done right if the delete-message pin was used.
  I modified notification.py to emit a signal if a message has been deleted and
  conected this signal to gmoccapy.
- corrected also a small mistake in _show_errors, it was posible to get messages
  without text, added a default text.
Merge branch '2.6'