Assets added, Actor framework working

The big commit here is all the assets for the demo game. Lots of files.

The other news though is we are currently loading a sample xml file with
a single actor in it, which then calls into the Actor Factory to build
it. It's returning empty pointers at the moment because the work of
parsing this out is big in and of itself. But we now have an idea on how
levels are going to be loaded into the game.