Report incorrect feature codes used in armory search

[mathghamhain]

If you do an armory description search for FOOBAR you'll get an error message telling you that FOOBAR is not a valid description!.

However, if you do an armory search for CAT:foobar you'll get a list of all felines, with no feedback telling you that :foobar isn't a recognized feature.

When doing a complex search with multiple criteria it's very easy to overlook a minor spelling or formatting error in one of the lines and get many more results than you expect — for example, if you search for PFESS:argent:~ and sable you'll get results that don't contain any sable because the proper search term is ~and sable without a space after the tilde, and the version with the space is silently ignored.