Anagram: allow for multi-word queries.

This still only returns single-word anagrams, but the query can contain multiple words now.

Also:
- Fix up the query triggers to be more sure of intent. 
- Caching enabled by default; turned off for "scrambled" responses.
- Add some internal caching for letter frequencies of dictionary words.
- Removed the ability to request "anagrams" of length less than th length of the query
Herein lies the rub.  The entire reason I got to poking around in here was because when I was fixing up the tests the other day, I was annoyed that "anagram of" triggered as a 'scramble to "fo"'....

I suppose I would be okay (for now) if I could just skip "of" and "for" at the start of the remainder.  Okay by you?