REIVEW: [NX-518] Orient database manager

This PR addresses the following issues:

https://issues.sonatype.org/browse/NX-518
https://issues.sonatype.org/browse/NX-519
https://issues.sonatype.org/browse/NX-542
I think we probably will expose richer pool configuration, but it will be opaque to the consumers of the api.  Ie. consumers still ask for named pool, and then the impl can lookup the configuration for that pool and return it.  Could even return a shared pool too, but I deferred that complexity until we get to the shared "configuration" database bits, at which point I think we'll probably implement something a bit more flexible.