German translation for getmonero.org

main:
 - [x] translated: de.yml - Status: peer-reviewed
 - [x] translated: lang\de\ - Status: peer-reviewed
 - [x] added: "de: Deutsch in other ymls"

resources:
 * untranslated: moneropedia - some terms added to match de.yml
 * untranslated: user guides
 * untranslated:  developer guides

Special thanks to ErCiccione and rodolfo912 as well as to rbrunner7