Changed the EmbeddedConnector framework to initialize all major components via configuration properties rather than through the public builder. This increases the size of the configurations, but it simplifies what embedding applications must do to obtain an EmbeddedConnector instance.
The DatabaseHistory framework was also changed to be configurable in similar ways to the OffsetBackingStore. Essentially, connectors that want to use it (like the MySqlConnector) will describe it as part of the connector's configuration, allowing more flexibility in which DatabaseHistory implementation is used and how it is configured whether in Kafka Connector or as part of the EmbeddedConnector.
Added a README.md to `debezium-embedded` to provide documentation and sample code showing how to use the EmbeddedConnector.
