JDBC connection and a Hazelcast client interoperability

[viliam-durina]

The JdbcConnection encapsulates a HZ client instance. If the user wants to use a HZ feature not available through JDBC, he has to open a new HazelcastInstance. There should be a way to do that with a single HazelcastInstance.

We should consider adding one or both of these:

• public API to get HazelcastInstance from a JdbcConnection
• add ability to create a JDBC Connection by providing a HazelcastInstance.

The latter is even preferable to handle special cases when we don't expose some setting, so that the user can create a HazelcastInstance himself and then create a JDBC connection by using it.