httpd: update Wicket libraries to version 6.9.1

Move to the latest version of Wicket.

There were a number of API changes which required minor tweaks throughout.  Also, something seems to have changed in the interaction between Java and the HTML markup to require certain specific css settings which were not previously required.

Testing done:

Reran all unit tests. Deployed instance and checked functioning and presentation webadmin interface and pages.

Target: master
Patch: http://rb.dcache.org/r/5781/
Require-book: no
Require-notes: no
Acked-by: Gerd