a client certificate may either contain `Create or `Force_create permission. If
the latter is used (vmm_req_vm --force), and a VM with the same name already
exists, this is destroyed (if the dynamic resources without the existing would
allow the new one to be deployed) and the new one is started.
I had this concrete deployment scenario, where kill ; create takes some minutes
since it is 10MB data which needs to be transferred from my laptop to a remote
server (me behind dialup).
- renamed `Image to `Create
- renamed `Destroy_image to `Destroy_vm
