i found that most man pages only had references to the main git-annex
manpage, which i stillfind pretty huge and hard to navigate through.
i tried to sift through all the man pages and add cross-references
between relevant pages. my general rule of thumb is that links should
be both ways unless one of the pages is a more general page that would
become ridiculously huge if all backlinks would be added
(git-annex-preferred-content comes to mind).
i have also make the links one per line as this is how it was done in
the metadata pages so far.
i did everything but the plumbing, utility and test commands, although
some of those are linked from the other commands so cross-links were
added there as well.
