Actor variation persistence

[Philip Taylor]

Save the actor variation for Entities and Nonentities when saving map files in the editor, and use them when the map is loaded.

Preferably, don't do it too inefficiently: don't store "Idle" for entities; modify the XMB format to have fewer redundant strings; and:

For objects which the designer wants to just be random, perhaps generate the initial variation pseudo-randomly and deterministically, based on a single ID number - then if the map is saved, it only has to save that number and not all the variation strings. (It shouldn't be a new random variation each time you load the map, because that'd be confusing when saving/reloading in the middle of a game and when doing multiplayer). The variation will become wildly different if the actor XML file is modified, but that is not very common and shouldn't matter.