MapperQuad does not seem to color correctly

When using the MapperQuad during rendering, the pseudocoloring based on a field does not seem to be correct.

To observe this, look at the baseline images for the MapperQuad test. The colors do not seem to match up the expected field values on the object.

In particular, take a look at the explicit3D.png baseline.

The colors do not match the range of the data and generally look off. Compare that to the equivalent explicit3D.png for the MapperRayTracer test.

This should be fixed, or if MapperQuad is unnecessary, it could just be removed.