performance improvement suggestion

This is just suggestion about performance improvement to use high level API of riak-java-client. Unfortunately, I didn't test this codes because I couldn't understand how to integrate HistoryGluon with Zabbix. However I think this is a good start of the improvement. 

This PR includes as follows:

- reduce call count of bucket props.
- switch list operation to streaming.

I hope this helps.

**requirements**

- riak-java-client >= 1.4.0