ThemeManager: German translation

Patch Set 1:     * initial commit
Patch set 2:     * minor rewording
Patch Set 3:     * make beginning of strings consistent
Patch Set 4:     * make wording consistent to AOSP
Patch Set 5:     * separate translations for phone and tablet
Patch Set 6:     * make wording consistent to AOSP (again)
                 * fix order of strings in product selector

Change-Id: I5d09a1af396104b3441fed1d47c78252e3a1d179