Bullet physics integration on Linux

Mostly just updates to cmake so it searches for all 4 bullet libraries and links the relevant 3 (or should it be 2?)

also bulletphysics.cpp had some windows style paths. Case-insensitive includes must be lovely...
Merge pull request #35 from tanderegg/develop

Fixed wgl glew extension problem
Merge pull request #36 from wrongu/develop

Bullet physics integration on Linux
Changed BulletMover to use a capsule instead of sphere
Fixed GLCubeSphere using the wrong texture index

GLCubeSphere was using the GL_TEXTUREX which indicates to GL when
binding a texture which slot to use. Instead it needs to set the slot
index.
Fixed bullet CMake on win32
Added the Latest bullet libs
GLCubeSphere now supports rotation on creation
Hide the mouse cursor
further linux fixes

* re-added the bullet include
* FULLSCREEN WORKS. this is exciting.
Merge pull request #37 from wrongu/develop

further linux fixes
Merge branch 'develop' of https://github.com/adam4813/Sigma into develop
Working on mouse rotation restriction
Merged upstream