REGISTRAR,GUI: new form item "auto-send button"

- When auto-send button is present on app form, it will
  try to submit itself once it's displayed.
  Validation of input is performed. If fails, manual sending
  is required from user.
- Added support to Registrar and GUI.
- Display help when creating new form item on widget selection.
Merge pull request #476 from zlamalp/autosend

REGISTRAR,GUI: new form item "auto-send button"