Split media and static folders

[Xpirix]

• This PR will prevent deleting files from media folders (cache, geopackages, models, packages, styles, wavefronts) when running python manage.py collectstatic --clear.

This is also for:

• No image preview for models and 3D models and they are not downloadable #298
• Our media and static are the wrong way around #114

Changes summary

• Use differents volumes for media and static in docker-compose for dev environment
• Add a command to collectstatic and delete folders from media that exist in static

Requirements on the server-side

• Update the docker-compose.yml for rancher to keep the current volume for media and use a different volume for static. For example:

volumes:
    - django-statics-data:/home/web/static:rw
    - the_current_volume:/home/web/media:rw

It's better to update this file in the code to match the configuration on rancher (confirmation needed)

• Restart the rancher server and run python manage.py collecstatic to generate the static folders inside django-statics-data
• (Optional) After making sure that everything is okay, we can delete all static folders inside the_current_volume by running cleanmediafolder

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a9dabb5) 36.97% compared to head (a36953e) 82.75%.
Report is 1 commits behind head on master.

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Additional details and impacted files

@@             Coverage Diff             @@
##           master     #340       +/-   ##
===========================================
+ Coverage   36.97%   82.75%   +45.77%     
===========================================
  Files         106      142       +36     
  Lines        4500     5497      +997     
===========================================
+ Hits         1664     4549     +2885     
+ Misses       2836      948     -1888     

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