Better error message when parsing malformed shadergroup commands
Proper exit and return code, rather than segfault, if testshade fails to set up the shadergroup
Make testrender accept new shadergroup syntax -- very readable.
Merge pull request #392 from lgritz/lg-group

ShaderGroup command parsing tweaks
Be more specific about camera attribute names
Re-converge some diverged bits of simplerend in testshade vs testrender.
In particular, microfacet closures, named transforms, and camera parameters
now work the same way in both.
Allow getattribute of camera attribs for testrender & testshade
and make a test for it.