ROOMBA_TASKS: hit wall during fleet management -> stopFLeet(true)

- hitting a wall during fleet management now stops the fleet by
  calling stopFleet with hitWall parameter as true. This enables
  an appropriate warning message to appear
ROOMBA_TASKS: Added FWSPEED to croiUtil (to help virtual testing)

- The speed that roomba uses when going forward (turning unaffected)
  in fleet management operations is now set in FWSPEED constant
  instead of a magical value.
- high value makes testing with virtual roombas more convenient