Simplifiy the 'angel installed' message

The pid of the angel is not displayed anymore:
- this was useful for debugging, but not anymore
- we now have commands to kill the angel without requiring to know its
  pid
- the user can easily get that info with bare 'ps' (as the angel is in
  the same process session, or with echo $APS1_PID
The name of the angel is displayed instead of the general command name.
Add 'Escape' utility for @PS1