Add a export task generation which is for cronjob usage

Currently work in progress: Print results on console.

How to run:
  python export_zip.py export_tasks
allow zip for allowed extensions
remove double task method
merge latest master
internal in memory zip creation
Merge branch 'master' into warm-up-export-zip
Make CSV and JSON processing compatible with merge of master

Also use new Flask-SQLAlchemy 2.0 behaviour.
Make JSON and CSV creation match the master branch versions.
Merge branch 'master' into warm-up-export-zip
put ZIP creation into RQ and scheduler
Use temporary files for internal JSON and CSV generation

Do not do any excessive memory usage anymore (up to 6-7 GBs on Crowdcrafting DB)
Avoid that whole PC hangs because of memory usage
Remove old export_zip.py
Upload ZIP files to internal export folder using uploader

Set timeout to 500.
Deactivate task-run csv creation for now because it creates 50GB ZIP files.
TODO: Refactor upload container folder?!
Fix insane 60GB local csv creation bug
ZIP creation in temp direcory with right CSVs now
use generated uploaded ZIPs for json
merge newest master RQ changes to this branch
provide CSV ZIP download from generated uploaded ZIPs
set ZIP generation to 24 hours
use app.owner_id for container
Merge branch 'master' into warm-up-export-zip-rq
first refactor. Put exporters in a class