mailu/setup/flavors/compose
Dario Ernst 9a440e2604 Force setup-file download scheme to HTTPS
Up until now HTTPS was only offered by redirect, making MitM possible
before server redirect hit the client.
Add scheme-force to HTTPS to the url-generation.

fixes 
..
docker-compose.yml Harden default configuration
mailu.env Fix ANTIVIRUS line in mailu.env file
setup.html Force setup-file download scheme to HTTPS