Allow multiple configurations of Narayana to execute in the same JVM

A long running feature request that I can't locate in Jira so recording here.

Future revisions of the application container WildFly would find it beneficial to run multiple instances of the transaction manager in different configurations (one-per app) and allow the service to be started/stopped/executed in isolation.

One of the barriers is that the factory method returns a singleton. The second is that there is static state in classes and so different configs are not viable.