Constructing global test interface for spire.
Working on batch renderer.

Still need to include appropriate frameworks and libraries, depending on
the platform.
Batch renderer correctly builds off-screen context on Mac OS X.
Removed SpireTester tool. Superceded by the batch renderer.
Making the uniform color a standalone test.
Combined header and cpp file for uniform color test.
Adding CImg to batch project in order to export images from OGL.

PerceptualDiff will be an external requirement if we want to compare
golden images at the end of the tests.
Fixed minor problems related to old TestUniformColor.

Also successfully integrated CImg into the project.