Context-Aware Configuration Referencer Provider

in context of provided a PR for a ReferenceProvider implementation for context-aware configurations:
https://github.com/wcm-io/wcm-io-caconfig/pull/17

ConfigurationReferenceProvider implementation of ReferenceProvider to return the reference context-aware configurations to the ActivationReferenceSearchServlet which allows the editor to publish the configurations along with the pages they are used in.