Don't show anything category-related if no categories defined.
Add basic ngrams support to the WordFrequencyAnalyzer.

This still needs inclusion/exclusion list support, which is
explicitly disabled for now.  It also hasn't been wired into the
job UI yet.
Add spec for n-gram support in WFA.
Add basic support for inclusion and exclusion lists on n-grams (#24).

This needs to be documented better, and it needs specs, but my
flight is about to start boarding (airplane coding is best coding).
At least the change hasn't broken 1-gram behavior, which *is*
tested in the spec.
Fix exclusion and inclusion lists, add spec (#24).