[Java container] Added jarUrl option to JavaContainerConfig

Added `jarUrl` option to `JavaContainerConfig`, so folks can install jar into Java Container the same way they install jars via `install-jar` command. For example to map the following command...

    process:install-jar -m com.my.Main my.group.id my-artifact 1.0

...to Java Container managed jar, we now can specify the following properties in `io.fabric8.container.java.properties`:

    mainClass=com.my.Main
    jarUrl=mvn:my.group.id/my-artifact/1.0