[WFCORE-161] Use ModelControllerServiceInitialization to provide JMX root access to the model

This replaces #199 which was problematic because it introduces a basic behavior change to how reads of the model were handled. This relies instead on the ModelControllerServiceInitialization API that was created for patching in order to provide a closer integration with the management model for optional core modules, beyond what is available to Extension impls. Only modules that are depended upon by the server or hc module can utilize this mechanism.