GitLab

This ports the Privacy Policy 1.0 from the wiki to GitLab and Markdown. The version 1.0 was already pretty good, but there were some major changes. The proposed version should include all important points from svenstaro's draft (and more 😉), all comments from its review were addressed.

Some things to remember before merging:

• the date when the updated policy becomes effective needs to be set in the "Version" section
• the policy states that a "news" item should be posted when the updated policy is released