Online documentation

The next release of Modoboa is coming soon and at last, I've taken the time to create an online documentation. I'm using sphinx to generate the HTML part.

You can browse it here. There is also a link on this page (look at the 'Links' box on the right column).

Currently it contains only explanations about installation and integration with other components. I'll add content about how to extend Modoboa with plugins soon.