Merge in first revision of outer loop component support

[scottkurz]

E.g. scottkurz/devfile-stack-intro@3f63642

Thinking that we might include in our devfile EACH of a 1-stage, 2-stage outer loop build.

So the user could have the choice of:
1-stage: mvn package && odo deploy
OR
2-stage: odo deploy

Fleshed out a bit..the 1-stage one probably has the Dockerfile provided by the app repo, e.g. like the one the OL starter will generate into a new project. The 2-stage one is purely online, tucked away in the repo/GH release and referenced remotely.
It certainly doesn't have to be all polished to keep up in this back burner mode. But it might be nice for someone else taking a look at our devfile to see our rough thoughts for where this is headed reflected within

[scottkurz]

Maybe a better breakdown is:

1. app-provided Dockerfile vs.
2. stack-provided Dockerfile (which is a 2-stage one)

E.g. if you had a 2-stage Dockerfile in your app repo.. you could do odo deploy just fine..just like in a 1-stage. We don't know when it's time to call odo deploy e.g. do you have to mvn package first or not?..but the user does.

And for our built-in Dockerfile to work from as small a dependency set as possible.. we use a 2-stage one like the one we've been using. So the only dependencies are git and docker/podman .. (No need for mvn which is built into the image)