Specify Fetch.size at dbFetch runtime

The fetch.size argument to the dbFetch method allows the end user to specify the desired fetchSize for the JDBC driver. If the argument is omitted, the rs.fetchSize is not set. This will then use the default fetch size (10 for Oracle, for example).

Additionally, if setFetchSize is not supported, the argument can be omitted.

This has been tested with with the SasShare driver and the Oracle Driver.