About Article modularity

[sveetch]

Zinnia have a nice feature for Article model modularity with a setting to use a custom Article model to include or change basic features without to duplicate zinnia code as an "in project" application.

However it brings some more work and i don't know really yet how to test it correctly so i dropped it since it is not fundamental.

But it would be nice to think about it.

[sveetch]

This is something that should be done during Beta stage since it will involve breaking changes.