communities: initial release

* Introduces communities module.
* Includes tests for views and Community model.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Co-authored-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
formatter: templates modularisation

* Creates base templates for brief and detailed
  HTML view.

* Separates css for formatter templates.

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>