Update German translations for 2.8.

Task-number: QTCREATORBUG-9712
Task-number: QTCREATORBUG-8923
Change-Id: I04367cf56be533cc8d078bb232362de9e5cbfe95
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
Reviewed-by: Robert Loehning <robert.loehning@digia.com>