Force that every project belongs to a workspace

[fwuensche]

If all projects belong to an organization, we can further simplify the back-end.

Additionally, since the organization authorizations logic is already implemented, we'll automatically improve the onboarding workflow, which now requires a manual intervention to create the Organization.

From now on, I believe the Organization should be created at the moment of the push.

And we should maybe rename Organization to Workspace, since personal projects would be added to an Organization named after the User.