Fixed a bunch of annoyances with date fields. The most egregious was the requirement to see, and to enter, dates in the format 1790-00-00 in cases where the precision was only to the level of the year, despite the fact that the JavaScript date validation code would mark this as an invalid date because of the zeroes. Partial dates without zeroes are now permitted, and filtering by date also now works properly.

Also realized that the search.php page has never had a working tab system, so you can't look at the search instructions. Hived those off to an include to get them out of the page (they may differ between projects anyway), and then fixed the error. It was due to the tab-handling JavaScript having been updated when the enter.php page was rewritten, changing the form of element ids; I'd failed to update the search.php page at the same time. Nobody noticed this. I guess nobody reads instructions.