Env cmd manual

This work removes the dependency that the manual provisioning had on the environment name.

Instead, the provisioning requires something that supports the API it needs to call.  This means that the interface that the add-machine command depends on needs a few more methods.

The AddMachines client method is now used, and the 1.18 fall-back code is removed.
Is this part of a larger decision to scrap the 18 interface ? If so, please publicise this as we have parts of 1.18 and 1.16 still in the codebase