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
This depends on where the new "git guidelines" outlined by Timo fit best. I think it is better to put them easily accessible on the homepage instead of into the offline documentation. Furthermore, svn.html solely explained the layout of an svn repository (trunk, branches, tags)...