Recast part 1: librecast

Adds Recast/Detour library code in the Engine/libs directory, and a project generator module to include this code as a library. Huge credit to Luis Rebollo for showing me how to make this work.

I've decided to submit three pull requests for recast since there are three distinct sets of changes to be made.
 1. This request, adding Recast library code
 2. #432 Making changes to the Torque engine to accommodate getting polys for Recast
 3. #433 Actual classes that wrap and make use of Recast/Detour
I figured it would be easier to break these up - especially number 2, since people will probably have differing opinions on my changes.