Holodeck

I originally was just going to make it so that people float in holospace, but ended up making a bunch of changes.

* People should now float in the holodeck "Space" scenery.
* The holodeck uses power, and shuts off if power is lost.
* Fixes carp being deleted when the scenery is changed. Instead, a holodeck subtype is used (uses the AI carp icon).
* Holocarp are friendly and cannot leave the holodeck unless the console is emagged.