dcache-webadmin: reformat html pages

Wicket mark-up was messy.  All html resources for webadmin have been reformatted for regularity and readability.

(The extra indentation is easier to maintain in my HTML editor.)

Testing: Redeployed and checked webadmin pages.

Target: master
Request: 2.7
Patch: http://rb.dcache.org/r/6077
Require-notes: no
Require-book: no
Acked-by: Tigran