Do not deserialize StringRedisConn pipeline/tx results by default

- Change StringRedisConn to not deserialize pipelined/
exec results by default

- Remove option to enable/disable deserialize of
results in StringRedisTemplate. In most cases, the
same StringRedisConn is not used b/w ops in a pipeline 
or tx, so this is rarely useful
Fix NPE on deserialize of Tuple values in tx/pipeline

DATAREDIS-229
Add deserialize of exec results to RedisTemplate

DATAREDIS-228

- RedisTemplate.exec() will now deserialize raw results
using RT serializers, where applicable. This behavior
is disabled if convertPipelineAndTxResults is set
to false on the ConnectionFactory

- Add new RedisTemplate.exec(RedisSerializer) method
that will deserialize all results using the provided
serializer.