Provide RxJava2-JDBC on top of R2DBC

This ticket probably defeats its creation as this project is also about JDBC.

Have you considered providing this library on top of a truly reactive database integration such as R2DBC? RxJava2-JDBC comes with a decent API for database access, however, JDBC is blocking and JDBC on ThreadPools comes with severe scalability limitations when talking about non-blocking reactive programming.

You already have all you need for proper non-blocking data access except the transport-layer. R2DBC is based on Reactive Streams. With RxJava2's `Flowable`, there seems be missing just a to adoption.