.gitignore: Add backup files

Some editors, for example Emacs and Vim, use "filename~" and
"#filename#" for backups.
Add 'de' module for german version

(No content yet)
Add German translation of part 1
Add German translation of part 2
Add German translation of part 3
Add German translation of part 4
Add German translation of part 5
Add German translation of part 6
Add German translation of part 7
Fix missing spaces

Found by @HenningB and

    grep -r '//[^ ]' source/de
Small changes to part 1 of German translation

Suggested by @HenningB.
Small change to part 1 of German translation

Suggested by @HenningB.
Small rephrasings in part 2 of German translation

Suggested by @HenningB.
Quote identifiers in German translation

Suggested by @HenningB.
Uppercase "Typechecker" in German translation

Nouns are always uppercase in German, even if they come from English ;-)
Change quotes in part 3 of German translation

See 5110a3d - we should be consistent in the use of double, not single
quotes.
Fix English word in part 6 of German translation

Found by @HenningB.
Small change to part 1 of German translation

Suggested by @HenningB, only partially done in 35d14f9f85adfdaf43d3d3a35ab4342292554f19.
Merge pull request #3 from lucaswerkmeister/1.1-german

Add German translation