Subshell commands for container management

[gonzolively]

In its current state, the ocre-runtime does not have a way to load container images pragmatically as users have to "bake in" their container by converting the WASM module (output after build time) to a hex array in src/main.c.

Recent discussions have us leaning towards an approach where we develop some Zephyr subshell commands to help with managing containers on an ocre-enabled device. The workflow would look something like this to get ocre containers onto an ocre-enabled device:

1. The user builds a container image.
2. The user uploads their container via the ocre cli (e.g. ocre push image-name:[tag]) to a registry of some sort
3. On the device, user loads the container onto their device by issuing a command, complete with an endpoint where to grab their container image from. (e.g. ocre run image-name <URL>)

[johnwalicki]

#3 Potentially follow the docker conventions where the image-name can be fully qualified.

	ocre image pull  "repositoryName"/"imageName"[:tag]