gh-44 Constant occupancy workload (sears)
gh-45 Modify DB API for efficient large object support (sears)

gh-45 Modify DB API for efficient large object support (sears)

 1) Add Makefile.download-db-libs, which downloads + unpacks all of the dependencies.
 2) Fix build.xml so that downloaded libraries don't break ant doc
 3) Add dbcompile-all target that builds all of the client libraries at once.

change DB API to use ByteIterator for fields instead of String.  This fixes a number of scalability problems.

NoSQL databases are capable on sub-millisecond latencies and YCSB
was only measuring times with millisecond granularity. This caused
transactions that took place in less than a second to be recorded
as taking 0 time to complete and as a result had the potential to
skew test results. This fix changes the timing granularity to
microseconds.

Add simple sharding capabilities for JDBC driver

Merge branch 'Cassandra0.8Support' of git://github.com/joaquincasares/YCSB into joaquincasares-Cassandra0.8Support