parent record with all null values (left join with no match) should be left null
added REUSE_STMT flag and related arg
removed LIMIT and OFFSET flags (always supported), added IS_CLOSED flag,
added a way to set type converters based on db column type name;
added getConnection and getResultSet (for underlying jdbc objects),
added ESCAPE_PATTERNS flag
use type in toString if typeName is null
added some informational methods