Priority areas
Merge pull request #236 from pgiraud/task_priority

Task priority
Adding message table to model
Send message to users when invalidating tasks
Fixing alembic revision
Fixing cache issues in task views
We don't use log for now. Remove it
Flake8 compatible
With tests
Resolving alembic branches conflicts
Merge pull request #245 from pgiraud/invalidation_messages

Invalidation messages
Export to GeoJSON