Add webinterface to manage emails

[pierreozoux]

Transferred from: https://github.com/IndiePaaS/IndiePaaS/issues/72

planned on RoundCube: http://trac.roundcube.net/ticket/1486582 the old:

• Postfix admin
• cyrup

the new:

• vimbadmin
• posty
• mail-in-a-box
• modoboa