DDF-527  created PersistentStore API that hides usage of Solr and Cassandra
DDF-527  added NotificationListener that uses PersistentStorage API
DDF-527 changed suffix to _txt_set for Solr schema multivalued and copyfield capability
DDF-579: refactored persistent storage API and impl to platform app
DDF-579:  added ID field to Notification event object