Refactor and extract BuildService #1115
Description
In order to be able to reuse the <build> configuration also from other tools / libraries than this Maven plugins and in order to provide additional ways to create OCI compliant images, the build service needs to be put into an interface and implementation parts specific to Maven and Docker needs to be separated.
If this is completed, these parts could be moved to fabric8-kit for reuse e.g. in fabric8-maven-plugin or maybe even a new image-maven-plugin (or oci-maven-plugin) which deals only with building images.
The tricky part will be how to split up the parts that are used by both, the build and run part of d-m-p. This might lead to some duplications of simple utility methods.