German online help for 8.4, round #1

OXUD-1067 Story OXUI-994 UI-Redesign: Notification area overhaul, round #2
OXUD-1069 Story OXUI-995 As a user I can configure a default signature for all my mail accounts, round #1
OXUD-1047 Story OXUI-985 2nd iteration of New Search (add visual filters)
OXUD-1066 Story OXUI-999 As a user the Settings App is shown as a modal dialog
OXUD-1068 Story OXUI-986 As a user I can search in settings
OXUD-1078 Minor updates due to minor UI changes