Wait for machine create & destroy completion

This release ensures that the provider waits for machine create & delete completion by having Terraform retry those resources until they have successfully completed. Before, success was reported just by the API response success, rather than a machine being in "ready" state on create or fully gone on delete.

This means that this provider can now be effectively used for conventional automation on top Paperspace machines. Note that in conjunction with providing a script resource, you can automatically add ssh-keys to machines.