Offline-documentation cleanup

This patchset cleans up the offline documentation:

 * Update old references to svn with references to git

 * Remove direct links to online resources - Those do not belong into the
   offline documentation, and are already easily available on the homepage.

 * Remove stub content that only pointed to online location

 * Unify indentation stuff
I disagree with the hassle of having to maintain these links. I find it irritating if information that is relevant at one place is not linked to from there but for which one has to search elsewhere. (I'm not saying that there isn't any cruft in our doc/ directory, and you clean out a good share of it; but I don't see the need to remove all of these links where they are appropriate.)