Optional Flexy Pool integration

[johnament]

https://github.com/vladmihalcea/flexy-pool/blob/master/flexy-hikaricp/src/test/java/com/vladmihalcea/flexypool/config/FlexyPoolConfiguration.java

You can use Flexy Pool as a wrapper around HikariCP. This is a general example, but spring based. It should be possible to use Flexy Pool as a wrapper around the existing HikariCP integration, if Flexy Pool is present.