Updating the site privacy policy

[hartenthaler]

The privacy policy needs to be rewritten. The current version was "quick and dirty" and does not comply with GDPR, as it does not allow you to use the site and disable tracking cookies.

see #5272

[fisharebest]

Also, see #5272, it needs to reference

• map providers
• Google charts (although there are plans to replace this with chartsJS)