Return success status from openSubdiv_finishEvaluatorDescr()

Before this change the given function used to fail silently in
cases topology is bad or uniform evaluator initialization failed.
This used to leave evaluator in a state which is not usable for
further processing but callee function would never know this and
will likely crash later when evaluating subdivision limit surface.

Ideally error message or code need to be passed to the calle, but
that's marked as TODO for now.
Added an option to FarMeshFactory to generate triangle patches instead of quadrilateral patches for a uniformly subdivided mesh.  This option is applicable to GL-ES, which does not support quadrilateral primitives.
Added a public constructor to OsdMesh that initializes the members objects from its arguments, allowing those members to be created by a subclass or an external function.

* maintainance work on the D3D11 specialization of OsdMesh to bring it in line with the other template specializations
* updated the facePartition example to derive PartitionedMesh from OsdMesh in order to allow other vertex buffer and compute controller configurations
Merge branch 'release/v2_4_1' into dev
Merge pull request #285 from nathan-at-digitalfish/add_osd_mesh_ctor

Add a public constructor to OsdMesh
Add missing third parameter to templated OsdDrawContext usage, caught in Presto build.
Merge pull request #280 from Nazg-Gul/dev

Return success status from openSubdiv_finishEvaluatorDescr()
Changes to address comments in #284.

* rolled getNumFVarVertices into allocateTables
* renamed tessellate to triangulateQuads (technically speaking, Loop scheme uses a trivial triangulation)
* condensed the pointer arithmetic used for triangulating the data tables
Merge pull request #284 from nathan-at-digitalfish/add_far_triangulate

Generate triangle patches for a uniformly subdivided mesh
Fix Windows build warning in FarPatchTablesFactory
Fixes a bug introduced in 808aabf that causes OsdUtilPatchPartitioner to fail to rebuild the face-varying data table correctly for triangle patches.
Merge pull request #289 from nathan-at-digitalfish/fix_fvar_triangulation

OsdUtilPatchPartitioner failure for triangle patches
Fix shape_utils genRIB function to use streams correctly.

fixes #290
Adding a PullDown widget to our HUD in examples/common

- adding pulldown type menu selector
- updated shape selection to use the new widget in various Gl examples
Additional GUI updates to GL example code

- switch Compute selection to pull-down menu
- add TBB controller to ptexViewer
- small cleanup in Hud

note: shading should also switch to a pull-down
More cosmetic changes to the examples GUI

- switch shading radio buttons to pulldowns
- re-ordered elements on screen in most viewers

note: the ptex viewer has not been updated to the new look yet
Adding a NO_MAYA flag to CMakeLists to disable all Autodesk Maya dependencies in the build
Cosmetic fixes to the ptexViewer example GUI

- switch to pulldown widget
- move GUI components around
- add TBB as a compute controller
More cosmetic fixes to examples' GUI

- fix default selection for pulldown widgets
- move widgets around to prevent overlap in examples
- add a little triangle indicator to the pulldown widget
- switch color from white to yellow for selected pulldown item
Fix OsdUtilRefiner incorrect "Invalid size of patch array" error reporting.

The size of the patch array can only be checked in uniform mode. An argument can be
made that this should be an assert...

fixes #292