95% done with Turret.

Tweaked Michael's 'py_saltPellet' code to make the object a ghost until
it's not touching anything. This helps my turret fire correctly.

Also, added code to the Turret so that it's the 'Turret' that fires, not
the ant-hill.

Finally, added code so that the Turret can be shot/disabled and
'collected' by the player when gooed.