revamping w3-recs: new specs, misc improvements

After quite a lot from my initial adoption, I've spent some time to update w3-recs.

Beside the long overdue update of shipped recommendations (quite a few new specification was released, mostly related to SPARQL, but a few more have been edited, including CSS 1 and 2), I've also uploaded some pending improvements. A couple of bug fixes were about dangling links and registration of recommendations with the GNOME devhelp stuff.

Additionally, I've also moved all the documents registered with doc-base under the new Help/Standards section of doc-base, which seems to be fit for W3C Recommendations. Apparently we have finally managed to have a proper section tree for doc-base, the decoupling of that tree from the Debian menu one will not be missed (at least not by me).

During the process I've also discovered a (recent?) change in debhelper semantics. Thus far I used to have broken doc-base document IDs in w3-recs, as they contained uppercase letters, which are prohibited according to /usr/share/doc/doc-base/doc-base.txt.gz. My fault, I concur, but in the past the documents got installed anyhow without any problem. On the contrary, with the latest debhelper all documents got written to the very same file, apparently stripping away the part of their names which do not match the used lowercase regular expression. Well, not too bad, I fixed one more bug, but with a warning fixing that would have been quicker.

Also, /me wonders, if everything (but package build :-) ) worked properly with uppercase document IDs, why the heck one should forbid them in the doc-base specification?