Change configuration to use composite memory/postgres plus solr persisters by default.

This MR changes the default Valkyrie configuration to use a composite persister metadata adapter for each of the environments (development, test, production). For the development and production environments, the composite persister metadata adapter (composite_postgres_solr_persister) persists to postgres and Solr. For the test environment, the composite persister metadata adapter (composite_memory_solr_persister) persists to memory and Solr.