Settings: Update German translation

Patch Set 1:    * add translation for 'Advanved reboot'
                  http://review.cyanogenmod.org/#/c/32093/

                * add translation for 'Volume adjust sound preference'
                  http://review.cyanogenmod.org/#/c/32043/

                * rename some strings

Patch Set 2-3:  * rename strings after comments
                * fix typo

Change-Id: Ia3cf0fee64f2a7bd6249d844cd05127c19d786fa