Bug 21497: Correctly format dates for ILL requests in OPAC

Bug 21497: Correctly format dates for ILL requests in OPAC

This patch updates the opac ILL template to use the $KohaDates plugin
for displaying dates. Also updated:

- Added "title-string" sorting to allow for correct sorting of dates in
  the table of requests.
- Corrected capitalization as per our capitalization rules.
- Added self-closing / to inputs as per coding guidelines.

To test, apply the patch and log in to the OPAC as a user who has
multiple outstanding ILL requests.

 - In the table of ILL requests, the "Request placed" and "Last updated"
   dates should be formatted according to your system's dateformat
   preference.
 - Sorting of those columns should work correctly.
 - View a request and confirm that "Request placed" and "Last updated"
   dates in this view are also formatted correctly.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>