[de] Use typographic dash and single/double quote

Instead of - and ", let’s use the typographically correct versions when not in code.
[de] Use Du, Dein instead of du, dein

The README states that this is the preferred spelling.
[de] Use dass, sodass instead of daß, so dass

Sticking to the new spelling.
[de] Use Dir instead of dir

The README states that this is the preferred spelling.
[de] Use ss instead of ß, when appropriate

Sticking to the new spelling.
[de] Use Dich instead of dich

The README states that this is the preferred spelling.
Merge branch 'next' from mynetx

Conflicts:
	de/01-introduction/01-chapter1.markdown
	de/08-git-and-other-scms/01-chapter8.markdown
Merge pull request #595 from progit-de/master

[de] Fix several typos because of new german spelling rules