Add support for multi sites

[vdboor]

I'd love to have support for managing multiple sites in the same system;
view all sites at once, or browse per site.

[vdboor]

in the works in git master!

[mrmachine]

Any accompanying docs for this feature? :)

[vdboor]

Docs are not yet ready, something I definitely want to see completed before a release happens.

This week I'm testing the new code on another client website, see what else is needed. Right now the admin only filters on the SITE_ID. When you run the project with different setting files and SITE_ID (or use django-multisite) you should get different contents.

Both django-fluent-pages, django-fluent-contents and django-fluent-blogs have been updated for this.You'll need the git master for both 3 (and django-parler git master therefore)

Editing multiple sites from the same admin is currently not included, but something I'd love to see in the future as well.