Some general site health improvements and bug fixes for stuff that I fished out of the error logs:
- redirecting old contest meter graphics to 404
- redirecting old-style forum topic links to current format
- added universal 404 handler to forum pages
- fixed site-crushing url; googlebot found some screwy link in the wild that looked like /part_details/parts, which resulted in the back end trying to load every part record at once. I think this might have been the source of the occasional site outages we've been seeing
- redirecting missing_info page for non-existent users to 404
- fixed exception in bbcode for potd tags that refer to non-existent part records, and another for POTDs that don't exist
- fixed another long-standing bug that we somehow never found before: if you set a mold id on a part, then later clear it, the "base_mold_id" that we use for populating the shared mold list was never getting cleared.
- updated the user profile links on the /collectors page
- made the parsing of tech spec rating bbcode more robust; you can now use rating=strength syntax, as well as rating name=strength
- fixed page crash when creating a new part record
