Replace cloudfoundry-runtime with Spring Cloud.

This PR removes cloudfoundry-runtime in favor of Spring Cloud for detecting and wiring service connections for bound services on Cloud Foundry. 

This change puts the responsibility of creating the DataSource on Spring Cloud, as opposed to just getting the connection details and creating the DataSource in the application. This has the benefit of making it easier to support connections to other databases, as Spring Cloud will create a DataSource for the type of RDBS bound to the app. 

Spring Cloud will detect a JDBC connection pooling provider on the classpath and create a pooled DataSource as appropriate. The application verifies that the Tomcat connection pooling DataSource was created so it can be further configured. 

cc: @ramnivas

Fixes #343.