Define a Developer (autoexport targeting) MergedModel using a mix of classpath modules and source modules specified at startup

For the developer workflow using auto-export, we want to define a full configuration model that is composed of some packaged config modules from the classpath and some source modules loaded from the local filesystem. The source modules should be defined using startup parameters passed to tomcat via the cargo.run maven profile.

This story will include the work to define these parameters and pass them into the runtime for the hcm-demo project. A separate story TBD will be needed to provide the same parameters in the v12 maven archetype.