* Increment Accumulo Version to 1.6.0
* Fix accumulo dependency versions
  - Harmonize guava version for Accumulo.
  - Automatically manage slf4j version.
* Clean up depr. code
* Clean up return codes and error logging

Make the batchwriter's number of threads configurable.

clean up dead code in client.

Based on YCSB++

http://www.pdl.cmu.edu/ycsb++/