Update images to have feature.sh like Open. Liberty images

[NottyCode]

[leochr]

Create a new kernel image to follow the application image pattern of Open Liberty (add server.xml, call feature.sh, add app and then configure.sh): https://github.com/OpenLiberty/ci.docker#building-an-application-image

As this would be a breaking change, use a new tag name (kernel-slim) - similar to Open Liberty. The kernel tag would be deprecated.

[leochr]

features.sh will be introduced as part of existing kernel images. If features.sh hasn't been invoked, then invoke it as part of configure.sh. Document the new process to build application images with features.sh (similar to Open Liberty)