collada support

Allow multiple asset loaders (one per asset type file extension).

Parse a collada dae file into a Mesh.

I'm not completely sure how to add eaxy-0.1.jar to the project.   I just dropped it in as engine/libs/eaxy-0.1.jar during development.

It's under a BSD license 

https://github.com/jhannes/eaxy/blob/master/license.txt

and it's from https://github.com/jhannes/eaxy.  I built it from source using maven.  The pom file is here:

https://github.com/jhannes/eaxy/blob/master/pom.xml