Make a Django-CMS plugin

[sveetch]

Is your feature request related to a problem? Please describe.

One of Lotus goal is to integrate properly with DjangoCMS as an optional feature. Although it works well, it lacks of
CMS plugins and CMS apphook to fully integrate.

Describe the solution you'd like

We need to do so in an additional and optional package like "djangocms-lotus" that will:

• have a CMS plugin to include articles in a cms page;
• have a CMS plugin to include category list in a cms page;
• have a CMS apphook to integrate Lotus as a CMS page;
• perform again the admin override that seems overwritten by admin-style, currently it results on Article and Category change form in admin to lack of additional buttons for translation and preview;

Describe alternatives you've considered
Include this in Lotus package itself, it would seem easier to do but won't viable on long term maintenance (cms part needs to fit to CMS versions support but Lotus has its own life that would conflict in the same package).

[sveetch]

At least we need a plugin to list "last X articles [for language]" and "Category listing [for language]".

Also an apphook would be very useful.