ColorCodes: eliminate NBS_ISCC sub dictionaries from lookups.

By their own documentation, the NBS submodules contain idiosyncratic
color names which are not well-suited to a general purpose color code
search.

In particular, NBS_ISCC::M contains a color called 'email' which caused
a confusing result for 'HTML email'.

The main NBS colors are included because they seem reasonable enough as
color names.

This fixes #490 and possibly partially addresses #454 and #442, I guess.
Sure, I like regression tests, but I didn't really come up with any reasonable looking queries with bad results.  I just have more like "wield color". It's hard to figure why anyone would ever do that search, except to check that they had made it stop working. :grin:

I'm hoping that by mentioning those other issues folks might show up with some other examples of queries gone awry.  I suspect this hasn't resolved everything, but I don't even know for what to look right now.