[admin] Add import/export admin feature to all models

[intrepidocabral]

This issue will be simple to handle, but in fact is not so easy and has more complexity by a number of reasons.

After research, the most plug-and-play app founded was the Django Import Export

It works fine, but we get conflicts with Django Reversion and Django Reversion Compare and it could be problems with other admin apps linked at the top admin apps panel. We bypassed this trouble rewriting the change_list.html admin template, following this sugestion: https://github.com/django-import-export/django-import-export/issues/287

This implementation was get sucess, but in some future point it must be changed to find a more pratical and right approach, something with no custom native admin templates or something well coexisting with other admin apps.

Done in:

• [x] Collection
• [x] Digital Assets Management
• [x] Event
• [x] Exhibition
• [x] Glossary
• [x] Location
• [x] Management
• [x] Person
• [x] Publication

[buccalon]

Export Ok Import bugado