Fix bug in cpuEvalLimitKernel.cpp

apparently an offset to a basis vertex was incorrectly set
WIP check-in for Gregory basis

Adding functionality to support the generation of stencils for the 20 CVs
basis of Gregory patches. This is still very rough... expect changes.
Adding visualization ability for Gregory patch basis to vtrViewer
Reordered refined face-varying values so those for each vertex are sequential:
    - added array accessors to properties of vertex values in vtr::FVarLevel
    - updated construction of base level face-varying topology
    - simplified population of face-varying properties in vtr::FVarRefinement
    - updated Far::TopologyRefiner::Interpolate/LimitFaceVarying() accordingly
Fixed bug in retrieval of FVar values for edge pair incident an N-sided face.