Status and Stop container, Destroy image

* Add a new command line option to return the status of the current dev container - if it's built as an image, running as a container, or stopped.
* Add a new command line option "down" to stop the current dev container. Verify it is running before attempting to stop it.
* Add a new command line option to destroy the previously built image. Verify that there is no container running that image and that the image exists before attempting to destroy it.