Enforce consistent standards for include order

[mposs00]

I believe the current proposal is:

#pragma once
Source header (i.e. Class.cpp's include of Class.h)
Project headers/internal API
Third-party library headers
Framework headers (not applicable here)
OS-specific includes (hopefully rarely applicable here outside of ifdefs)
STL includes

Someone needs to go through the existing source and header files and enforce this. We should also look into ways to incorporate this as a static check.