Created full text for user documentation in German.

Working on #39. The text is done in German. It needs images, and it
needs to be translated into english. Also, indexing doesn't seem to
work perfectly yet, so that needs some looking after. As a result, a
number of links does not work at the moment.
Updated german help files so the index can be created properly.

So that's how Apple help works. Fascinating. Now I just need the
screenshots and the english version, then #39 can be closed.