Add support for graph.RO_QUERY command

[filipecosta90]

This PR kicks off the support for graph.RO_QUERY command by introducing queryReadOnly(). It includes the same api methods that query() offers.

[DvirDukhan]

@filipecosta90

1. see comments
2. please add the RO API also to the transactions
3. I think that we need dedicated test functions for RO API instead of mixing with the current tests, which are messy

[tanvirp]

Will RO api work with read only slaves? Looks like

JRedisGraph/src/main/java/com/redislabs/redisgraph/impl/graph_cache/GraphCacheList.java

Line 53 in ed0c37c

ResultSet resultSet = redisGraph.callProcedure(graphId, procedure);

will eventually call

JRedisGraph/src/main/java/com/redislabs/redisgraph/impl/api/AbstractRedisGraph.java

Line 112 in ed0c37c

return query(graphId, preparedProcedure);

, which will issue the QUERY command instead of RO_QUERY command. I am not sure if this will be taken care in this PR.

[sazzad16]

@tanvirp Do you have a solution in mind? Feel free to craft a PR.