Optional Crispy form and CMS

[sveetch]

Currently both DjangoCMS and Crispy form libraries are package base requirements.

But concretely the application would be able to fully work without them.

We need to investigate and possibly implement these libraries as extra requirements when there are not present, the application should still run correctly.

• Crispy form (used for form layout);
• DjangoCMS (used for plugin);