Make Session an interface for easy decoration

[root-talis]

I have ran into a situation when I need to do two things:

1. Log all queries - for debug;
2. Make queries frequency report - for throughput monitoring, queries per second.

The most straightforward way to implement his would be to wrap the Session object into a decorator. In order to use Kotlin decoration syntax, both the original Session class and the decorator need to implement the same interface.

[vsch]

@root-talis, good idea.

• Fix: factor out Session and Transaction functions into interfaces. Implementation renamed
  to SessionImpl and TransactionImpl

I will be making a release 0.4.2 with these changes.

[vsch]

@root-talis, repo updated. Maven update done but will take some time to propagate.

[root-talis]

Thanks for the update! Works like a charm :)