settings: add voltage control to set on boot

Notice: all overclocking/undervolting stuff will not
be carried to the per-app profiles, since i don't
want this. The user should actively set something like
this.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
translations: update translations (english/german)

Signed-off-by: Blechd0se <alex.christ@hotmail.de>