* do not allow to obligatorily require contact information
* add remark that the data is provided voluntarily
* mention how to delete the data
* be very clear about the fact that the data being entered is public and
can be downloaded and processed by anyone.
Backport of Patch ab7f1acd to v2017.1.x
Based-on-patch-by: Christof Schulze <christof.schulze@gmx.net>
