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.

I'm not sure exactly how many items there are in that scene, but with 24 items the power usage should be 20kW. So I don't think the power draw will really get much higher than 25-30 kW, which isn't so bad.