Add a docker compose configuration and mailman-web

This commit adds a lot of new code including the mailman's web
frontend. It includes a configuration file which can later be
configured to run required configs.

Also, the docker-compose file spins off the containers, sets up
appropriate volumes and links.

core/assets/mailman.cfg

@@ -1,7 +1,11 @@
-[devmode]
-enabled: yes
-testing: yes
-recipient: you@yourdomain.com
+# [devmode]
+# enabled: yes
+# testing: yes
+# recipient: you@yourdomain.com
+
+[webservice]
+hostname: 0.0.0.0
+
 
 [mta]
 smtp_port: 9025