Add datepickers in advanced search, fixes #4666

Squashed commit of the following:

commit 2eac6de919830f82bca623c8bb1ea0a54da276d0
Author: Mike Gale <mikeg@artefactual.com>
Date:   Wed May 8 09:49:51 2013 -0700

    Added datepickers -- issue #5038

commit a7cfaf0e5ecd1ed3fdf3c43f90a5ddbb9ad5631d
Author: Mike Gale <mikeg@artefactual.com>
Date:   Mon May 6 16:49:36 2013 -0700

    Added help link in advanced search

commit aefcf9d08018582717f91847a3322f9bf4664df5
Author: Mike Gale <mikeg@artefactual.com>
Date:   Mon May 6 16:01:23 2013 -0700

    Move up date range box on page