Acceptable first pass at content test documentation.  En passant fixes.

 * runtimes.ini: clarify that version_adjust needs to work with py2.0;
   markup fix.
 * content_tests/stddef.ini, survey-scan: remove vestigial feature
   so I don't have to document it.
 * doc/conf.py: better pygments style.
need to ignore __pycache__/ for 3.3 compat
Restore the sidebar and much of the base Sphinx style.