Remove the ptex-specific code from the Far::TopologyRefiner and instead provide it in a separate class Far::PtexIndices. Clients who need to use the Ptex API need to first build a Far::PtexIndices object by providing it with a refiner.
This has the advantage of keeping the API on the TopologyRefiner a little cleaner. The ptex methods were const but were mutating state with const_casts. The new mechanism still achieves the same lazy initialization behavior by forcing clients to instantiate them exactly when needed.
A disadvantage of this approach is that the PatchTablesFactory creates its own PtexIndices and throws it out after the patch tables are created. This is great if you're never going to need the ptex indices again, but not so great if you will need them again.
Const' declared instances of Vtr::Array do not protect the pointer held
privately by the class properly. In order to force the compiler to
protect this pointer, we removed all non-const accessors from Vtr::Array
(now renamed Vtr::ConstArray) and moved them to a child class (Vtr::Array),
which requires const_cast<> operators internally to allow access.
The change & renaming is then propagated to all internal dependencies.
Make the sample locations dynamic by adding a velocity vector. Face boundary
crossing is handled using the new ptex adjacency functionality recently
added to the Far::TopologyRefiner.
