Initial functional checkin of the controller

Note: This does not yet handle artifacts, nor the logs from the builder-core, as we don't yet have those interfaces exposed
How does this variable get used?  I believe up until this point `docker-builder` has always expected the `Bobfile` or equivalent to be at the top level, thought that could change.  If the user is going to be providing this value, we will have to sanitize it (like https://godoc.org/github.com/sylphon/builder-core/filecheck)