Allow compositions of objects as one "shape"

[iksbob]

Where an object would normally assign a simple BSP to it's "shape" value, alternatively allow the definition of a daughter object or hierarchy of objects. Placement variables (x, y, z, pitch, yaw, roll) would be interpreted as displacement from the parent object's location. Motion of the mother object would affect the daughters, however the daughters should also move independently if the daughter object type allows it.

This might be asking a lot, but should be very powerful on the content-creation side of things. From simple copy-paste-tweak duplication of architectural structures, complex shaped wallDoors (think elevator car), fancy multi-segment extending bridges, guard turrets that change location on a set path, chimera boss enemies and so on.