Added BulletShapeSphere

This is a new collision component for sphere type objects.
Hopefully fixed mouse look issues with SDL
Removed SDL2_Image.lib from win32 projects

Added SOIL instead.
Added a Quit() method to IOpSys

This is a static method that must be defined in each derived IOpSys to
be specific. It is static to allow it to be called anywhere regardless
of having a reference/pointer or instance to an IOpSys.
Added some sanity checks to GLMesh::LoadMesh

When copying to the permanent buffers, the temp buffers are now size
checked.
Merge branch 'develop' of https://github.com/adam4813/Sigma into develop

Conflicts:
	src/os/sdl/SDLSys.cpp