Squash the f-docker-hostmachine branch.

Initial work

commands/up: make sure all names to with_target_vms are strings

providers/docker: create a docker host VM if needed

providers/docker: executor abstraction for driver to eventually support remote

providers/docker: vagrant executor

providers/docker: support creating the machine

providers/docker: status works if host VM is gone

providers/docker: use start fence to get real docker output

core: Call preserves stack ordering

core: support Message post option

providers/docker: Guard some features with HasSSH checks

providers/docker: much better messaging around create/destroy

providers/docker: output the container ID on create

providers/docker: copy the hostmachine Vagrantfile to the data dir

providers/docker: should make host machine before any up action

providers/docker: HandleBox before the host machine

providers/virtualbox: functional_vboxsf to disable vboxsf

providers/virtualbox: synced folder usable method should take 2 args

providers/docker: default machine name to :default
provisioners/docker: fix module name for new docker provider
Merge pull request #3484 from mitchellh/f-docker-hostvm

Docker provider spins up a host VM if necessary