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
@mwmiller I'd probably also `html_enc($w)` just in-case, really very *very* unlikely but you never know; if the scramble is stable, then it'd be possible to craft a request that'd reliably XSS