Update simpleCpu to use GLFW

In this change:

 * Fixed the linux build issues in the CMake files
 * Removed GLUT and replaced it with GLFW
 * Removed the apple-specific bootstrap (since GLFW as already required)
 * Removed HUD string drawing. This could be replaced in the future, but the mac version didn't have support for it before.

Also included:
 * Kill the GL viewer when the window is closed

Tested with:
 * OSX, GLFW 2.7
 * Linux (RHEL), GLFW 2.6

It would be great to get GLFW 3.0 and Windows test runs.

This partially addresses issue #117