Redis-adapter redis connection is not reused when RedisTable is created

When creating RedisTable via ModelHandler, it relies on an instance method RedisEnumerator#deduceRowType to extract field type map, redis connection will be established and closed every time a table is created, which is unnecessary and redundant, so simply make the method a static one will solve the problem and make it more performant. Actually, CsvTable implementation works the right way.