More specific selectors, javascript cleanup.

* Assigned jQuery selector results to variables for speed.
* Moved all .attr('data') calls to .data() calls.
* Added :data(uid) selector.
* Split the multiselect checkhandlers into separate functions.
* De-duped click event on password change/img.
* Used fluent interface on jQuery object for event binding.
* Removed redundant tag names in class selectors.
* Fixed incorrect date display for last login.
* Added Userlist.has() to search for uid.
* General code convention compliance fixes.

to-do: Group dropdowns currently don't add the admin group after the search result, not sure why yet.