Shuffle directories and filenames to get rid of historic cruft and to better reflect contrib/production status

 * Slight help for warden_curl_test.sh
 * TL;DR README section

Parent categories are now also saved in event_category_mapping, which simplifies fetch_events. Fixed AND->OR in group checking. Group now also matches only at "." boundary.

Auth for sending events fixed

Fixed multiple HTTP args encoding/parsing, store_event now uses SQL placeholders, more robust fetching of cat/tag in store_event, simplified map_id usage