- FarKernelBatch becomes a class w/ accessors
- split the FarKernelBatchFactory to its own header file
- add doxy doc
- propagate fallout to the rest of the code base
2 client APIs are changed.
- VertexBuffer::UpdateData() takes start vertex offset
- ComputeController::Refine() takes FarKernelBatchVector
Also, ComputeContext no longer holds farmesh.
Client can free farmesh after OsdComputeContext is created.
(but still need FarKernelBatchVector to apply subdivision kernels)