More work for  RMAN-16047. Only load grids if they haven't been loaded yet. Also, deal with string and boolean grid types.
More work for  RMAN-16047. Only load grids if they haven't been loaded yet. Also, deal with string and boolean grid types.

prman-pixar/RenderManForBlender,prman-pixar/RenderManForBlender,adminradio/RenderManForBlender