terraform: UIOutput interface
rpc: UIOutput
terraform: change provisioners to take UIOutput
rpc: implement provisioner update
command: set UIOutput
command: UIOutput is functinal
terraform: UIOutputPrefix
terraform: prefix the provisioner output
terraform: no longer require uiOutput, do it auto in Hook
command: compilej:wq
provisioners/*: new interface
terraform: comments
command: send the provisioner output to the prompt
Merge pull request #361 from hashicorp/f-provisioner-ui

Foundational support for UI output from provisioners