add shapes::computeShapeBoundingSphere() function
fix bug in box sphere calc
fix cylinder bounding sphere calc.
fix compile bug in computeShapeBoundingSphere for cylinder.

Also change variable names for clarity.
add unit tests for computeShapeBoundingSphere()
place generated config.h in build tree, not src tree.
Merge pull request #3 from acornacorn/master

Add function to compute bounding sphere of a shape