providers/docker: Fix SSH access to container when no Host VM is in use [GH-3799]
Adds minimal implementation to deploy a Salt minion on Windows including support for pre-seeding the keys
redirect output of mkdir statement to out-null in bootstrap-salt.ps1
sometimes salt-minion wouldn't start - this seems stable so far across 10 deploys
Retries starting the salt-minion service several times and adds elevated: true to salt calls
Remove Salt Master & Salt Syndic changes - not supported on Windows by Salt
Also copy minion config in bootstrap-salt.ps1 & update Salt docs to mention syndic/master not supported on Windows
minor indentation fix
Only try to copy keys & config if they have been uploaded
Fixed issue 3816

Elevated command line is now rendered to a script which is uploaded to the guest and executed. This allows the command line itself to be less than 100 chars to start the script and any user commands are puts into the script which has unlimited* length.
Wait for  to be populated & explicitly check for Running status of service
added capath option to curl Downloader
Now wait for service to be registered before trying to start it
synced_folders/rsync: dup arg list [GH-3864]
communicators/winrm: don't look up forwarded port if non-local [GH-3861]
core: don't port collision detect UDP [GH-3859]
providers/virtualbox: check VBOX_MSI_INSTALL_PATH on Win [GH-3852]
Merge pull request #3847 from mitchellh/command-line-too-long-fix-for-winrm

guests/windows: fix #3816 long arg list
update CHANGELOG
providers/docker: don't port map SSH if no has_ssh [GH-3857]