hlslPatchGregoryBasis.hlsl is an equivalent to glslPatchGregoryBasis.
Update dxViewer to be able to switch among bspline, gregorybasis, legacy
end capping.
also fixes a bug of GLSL legacy gregory shader which had an inconsistent
resource naming with example codes.
It looks like there's still an issue of D3D11 patchParam data fetching.
we'll come back to that bug.
Remove DrawRegistry from osd layer and put a simple shader caching
utility into examples/common. osd layer only provides patch shader
snippet and let client configure and compile the code. Clients also
maintain the lifetime of shader object, which is preferable for the
actual application integration.
update all examples to use the new scheme.
