Add debug command (to attach debugger, forward ports, etc.)

[scottkurz]

I'm a bit confused exactly how debug is supposed to work.. these links:

redhat-developer/odo#3187
redhat-developer/odo#3059

seem to suggest that you either push in debug mode or non-debug mode whereas going back a ways, this:
redhat-developer/odo#822
discussion suggests debug mode maybe should always be enabled.

As a stack user, the use case is simply to be able to connect an IDE debugger.

I'm not clear though if we need to force the user to restart the container in order to switch, or maybe if we'd only do that if we really wanted to optimize non-debug perf. startup time and run with -Ddebug=false.

(We may or may not include "debug configurations" for Eclipse, VSCode, etc. .. I'd probably break that out into a separate issue.)

More investigation needed, I started a Slack conversation here: https://openshiftdo.slack.com/archives/CR77F5GEQ/p1597930737002400

[scottkurz]

Watch this one too in the devfile repo: odo-devfiles/registry#39

[scottkurz]

Resolved by https://github.com/OpenLiberty/application-stack/pull/43/files