Metadata: MetadataGenerationSv as InitializingBean

Initialize the MetadataGenerationService as an InitializingBean to
address the comments raised in #157:

* removed commented-out constructor.

* implemented org.springframework.beans.factory.InitializingBean to get
  notifications after dependencies are injected.

* rename initializeRegInfoConfig() to afterPropertiesSet() to match the
  InitializingBean interface.

* drop the registrationInitialized variable tracking whether we have
  initialized.

* drop the calls to initializeRegInfoConfig() as the intializion gets
  called automatically after dependencies are injected.
** this also addresses the request to split the call onto multiple lines
   - the call has now been removed instead.

* and adjusted the spock test for the feature to force re-initialization
  by instead explicitly calling metadataGenerationService.afterPropertiesSet()