Switch to xstatic-bootstrap-datepicker

This points to datepicker 1.3.1 in xstatic.
Also fixes a couple of minor bugs in forms with
the new datepicker. The datepicker patch is:
https://review.openstack.org/#/c/116866/

Change-Id: I0a8cb7a16e50addbbdb10df8bdd4be427937bd81
Closes-Bug: 1361666
Merge "Switch to xstatic-bootstrap-datepicker"