Finish name changes
Re-work filtering and caching

* sx-auth.el
  - Use new symbolic cache access

* sx-cache.el
  - Implement symbolic cache access

* sx-filter.el
  - Use symbolic cache access
  - Compile and save filters on-demand
    (more work to be done to this end)

* sx-question.el
  - Symbolic filters

* sx-request.el
  - Protection against infinitely recursing when compiling a filter
    This will be re-worked into requests (a front-end function) and
    'raw' requests (a back-end function).  The front-end will add
    convenience to the back-end.

* test/tests.el
  Remove outdated tests
Delineate and alphabetize API symbols

It's ugly to look at, but diffs will be more precise.