LDAP authentication with Docker registry

See merge request !68

So we can just commit and push on the test machine without learning too much Git

This was annoying when testing stuff directly on pica01-test without having a commit.

Because IPv6 is not enabled inside Docker containers and it's more complicated than I thought, see later

This reverts commit b5054091.

[Mail] Partially revert e0260299 and make Postfix listen to port 25 again

See merge request !67

ps is needed for opendkim init scripts

See merge request !66

See https://team.picasoft.net/picasoft/pl/onwhgfw1pjgqpyubdq5xb3e8po