Add support for Narayana TM

[vladmihalcea]

The JBoss Narayana TM should be supported by FlexyPool, to make it available to JBoss and Wildfly Application servers.

[vladmihalcea]

I took a look on the Narayana codebase and it seems they don't really offer actual connection pooling (min/max pool size), as they just reuse one connection for the duration of the current Transaction.

The actual connection pool support resides in some other JBoss module and I found that you can configure external pools too (e.g. C3P0 or HikariCP). This could be a workaround for the moment, until FlexyPool supports proxying XADataSource as well.

The original implementation started with Bitronix, which doesn't require an XADataSource, since it can proxy any DataSource even in a JTA environement.