* Add german layout for redox keyboard
A german layout for the redox keyboard which tries
to stay close to the default english redox layout
while acommodating the umlauts at their usual position.
* Fix keycodes in german redox keymap
The keycode for Y was wrong.
* Minor changes
* Remove #ifdef include guard by #pragma once
* Remove unnecessary include from rules.mk
* Review changes
Remove unnecessary code fragments that
were pointed out in the review
of PR #3695 by @drashna.
