Refactor LogMinerHelper and SqlUtils

The LogMinerHelper class exposes quite a number of static methods that are used solely by the LogMinerStreamingChangeEventSource class. It would be more logical if those static methods were moved into the event-source class where used. Additionally, many of these methods take a raw java.sql.Connection but instead we ideally should be passing OracleConnection so that methods can take advantage or at the very least enhance the core repository's JdbcConnection where possible.