Use some of Vagrant's plugin machinery and some ruby metaprogramming to
activate the plugins. Make them experimental as long as this is still
work in progress and not very useful.

Use a secondary communicator to kill the job, which is as reliable
and much faster than the out-of-process solution.

Remove script before killing job to prevent deadlock, and kill
the entire process group.

Are combined with the machine matchers, which take precedence.

Can happen if thread execution raises an exception.

Add test, fix failures.

* map any location in host ~ to corresponding path in guest ~
* establish and revoke trust in create/terminate commands
* correct error message when host user has no public rsa key
* code cleanup: error type in correct module

Making a WinRM connection in the same process seems to disrupt the
current connection, so go out-of-process instead.

Fix some Ruby style

Fix deprecation warnings.

Don't remove them, mark them as disabled.

Needed by some linux distros.

Since it runs git commands to check out the latest tag, running the
entire script as sudo will break permissions for the clone.

The looping is done on the guest, so small overhead.
For Windows, support in addition a --console option which allows running
the job without the psexec detour.