[Bug 1874] See who's in a particular custom filter when posting

Conflicts:
	htdocs/js/jquery.postform.js
[Bug 1874] improved query methodology, closed some security holes and
added some error/sanity checking.  Also now sorts the final list.
removing superfluous <div>
Merge pull request #455 from woggy/thisisatestbranch

[Bug 1874] See who's in a particular custom filter when posting