Accumulo db driver for ycsb.

Based on YCSB++

http://www.pdl.cmu.edu/ycsb++/
Fix Accumulo retrieval of values for scan and read
Cleanup for move to Accumulo 1.4.4

* set .gitignore to standard eclipse
* update versions of Accumulo to 1.4.4
* Pin slf4j binding to 1.5.8

Accumulo, Thrift, and YCSB all use different versions of slf4j, causing
runtime issues because everything is bundled together. Pin the version
to something in the middle that seems to work, even if it's not the
latest and greatest version.
Update Accumulo version to 1.4.5.

clean up dead code in client.
Include an example Accumulo configuration file.

Make the batchwriter's number of threads configurable.
Cleanup and upgrade to work with Accumulo 1.6.0.

* 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
Merge pull request #170 from busbey/accumulo

Add Accumulo as a backing data store