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
Fix typo in redis/README.md
Merge pull request #173 from wuxb45/master

Fix typo in redis/README.md
Add an adapter for MongoDB using the asynchronous driver.
Allow setting the java version to use via the "JAVA_HOME" environment
variable.
Optimizations.
Add option: threadsAllowedToBlockForConnectionMultiplier
Update MongoDB Async Driver version.
Cleanup
Don't use finalizers to close cursors
Updated to current standard write concerns
No need to call getError on writeResult. any errors for writeConcern level will throw exceptions and be caught in catch block
Set default thread count to 100 when thread count is not specified
Added 'Install Maven and Java' instructions Ycsb config parameters
example