Fix LOD issues with RequestVolumeTraces and InterpolatingVolumeDataAccessor
- Improve SimpleRequestVolumeTraces tests so it takes LOD into account (but still only tests LOD 0 by default). Add new TestLODTracesRequest test based on Julien Lacoste's Java code that reproduced the issue with RequestVolumeTraces when LOD > 0.
- Fix RequestVolumeTraces when LOD > 0.
- Initialize VolumeSampler in InterpolatingVolumeDataAccessor correctly when LOD > 0.
- Use consistent capitalization of LOD.