[Self] VM creator

[pdonias]

• A VM created (or cloned/copied) with Self Service is marked as created by the user
• A super-admin can change the creator
• A snapshot of such a VM contains the creator info and restores it when the snapshot is reverted
• When such a VM is converted to a template, the creator is removed
• A replicated VM can have a creator which is the creator of the VM (not the creator of the backup job)

[olivierlambert]

Should we put this in v6 or not?

[pdonias]

We actually implemented the "VM creator" feature in #6771, but independently from Self Service. I think we can close this as done and see if we need the extra features (like a super-admin being able to edit the creator) in the future.