Add very basic support for command line only applications

[geoand]

Relates to: #284

This is probably wrong on a few counts since it touches core things that I'm not entirely familiar with.
I'm opening this however with the hope to get some feedback on the approach.

The basic thing the user would use is the CommandLineRunner, similar to what Spring Boot has

[dmlloyd]

I'm not sure this is the right approach for this kind of application. Let's discuss after the release.

[geoand]

I'm not sure this is the right approach for this kind of application. Let's discuss after the release.

This is reason I wanted to open the PR soon - to get feedback :). Feel free to reach out whenever you would like to discuss it

[geoand]

I also need to update this based on the new naming for deployment and runtime

[stuartwdouglas]

Please hold off until after we are done with release as our CI is backed up.

[geoand]

Sure thing 👍

[stalep]

Perhaps Æsh could be a good fit here. Quarkus could provide its own InvocationContext that is sent to the execution block for the command line application. Through the InvocationContext the command line app can automatically get access to whatever API Quarkus wants it to.
Also, Æsh will parse arguments and populate them into appropriate fields.

[geoand]

Superseded by #1301