Backfilled unit tests for Windows guest support

- Fixed typo in helper test
- Removed extraneous machine.config prefix from Windows guest config validation
- Added WinRM communicator unit tests
- Added Windows guest capability unit tests
Added WQL support to Vagrant communicator execute

- Removed duplication for WQL specific commands
Windows GuestNetwork directly uses the communicator

- Fixed slight Law of Demeter violation
- Make guest access through comm consistent
Cleaner DHCP detection for Windows guests
Added guest network tests for Windows guests
Added Windows guest file manager for recursive uploads

- Since WinRM uploads are so slow, MD5 content checking is used
Add WinRM file transfer error and english text
Merge pull request #3516 from mitchellh/backfill-windows-guest-unit-tests

Backfilled unit tests for Windows guest support
Merge pull request #3519 from mitchellh/windows-guest-file-manager

communicators/winrm: Windows guest file manager
Merge pull request #3517 from mitchellh/communicator-support-for-wql

communicator/winrm: Communicator support for wql