German Online Help for 8.7.0

- OXUD-1116 Story OXUIB-1902 Mail search in combination with inbox categories is confusing
- OXUD-1126 Enhance the description of App specific folder sharing possibilities
- OXUD-1127 Check the German user docu for missing translations
- OXUD-1129 Check the settings Docu for Guard and Documents
- OXUD-1130 Story OXUIB-2005 Searching All Folders excludes Spam and Trash folders
- OXUD-1132 Story OXUIB-2025 Default search does not find attachments
- OXUD-1133 Internal QA: Check for remaining inconsistent wording and other tiny issues