initial version of 'heightfield' devkit sample.
assigned default values to rarely-used arguments.
tweaked formatting.
added foundation::AttributeSet::reserve_attributes().
added renderer::MeshObject::reserve_tex_coords().
reserve texture coordinates before building the mesh, plus a couple simplifications after recent API tweaks.
added incomplete CMake file (missing OpenEXR dependency).
Merge branch 'master' of github.com:appleseedhq/appleseed
cosmetics.