Fix LOD rounding issues
- Remove commented out code that was used for reference when creating the TestVolumeDataReadAccessorLOD test.
- Add LOD rounding tests.
- Change voxel snapping for LODs in VolumeDataRegion constructor.
- Amend TestLODRounding/TestProjectedSubsetLODRounding.
- Fix effectiveOverlapMin/Max calculations and update ProjectValuesKernel to do correct LOD rounding.
- Fix VolumeDataPageImpl::WriteIntoLOD to do correct LOD rounding.
- Make it easier to debug TestProjectedSubsetLODRounding if it fails.