SWITCHYARD-1637 Add support for extension module slot option in subsystem configuration

Add support for extension module slot option in subsystem configuration

@mageshbk @kcbabo : Is there anything I need to do on the loading/deploying end here?    The slot is included in the module identifier, which seems like what they do in AS, but I wasn't sure if there was something I have to do in SwitchYardExtension.java/SwitchYardExtensionAdd.java/SwitchYardDependencyProcessor.java so that we discern between slots on loading/deploying.