Experimental support for PostgreSQL (#1525)

* Cash selection refactoring such that 3d party DB providers are only required to implement Coin Selection SQL logic.

* Re-added debug logging statement.

* Updated to include PR review feedback from VK

* Refactoring following rebase from master.

* Fix broken JUnits following rebase.

* Use JDBC ResultSet getBlob() and added custom serializer to address concern raised by tomtau in PR.

* Fix failing JUnits.

* Experimental support for PostgreSQL: CashSelection done using window functions

* Moved postgresql version information into corda/build.gradle

* Using a PreparedStatement in CashSelectionPostgreSQLImpl

* Changed the PostgreSQL Cash Selection implementation to use the new refactored AbstractCashSelection

node/src/main/kotlin/net/corda/node/services/persistence/HibernateConfiguration.kt

@@ -93,6 +93,7 @@ class HibernateConfiguration(val schemaService: SchemaService, private val datab
     // during schema creation / update.
     class NodeDatabaseConnectionProvider : ConnectionProvider {
         override fun closeConnection(conn: Connection) {
+            conn.autoCommit = false
             val tx = DatabaseTransactionManager.current()
             tx.commit()
             tx.close()