Refactor PerformanceEvaluation tool

PerfEval is kind of a mess. It's painful to add new features because the test options are itemized and passed as parameters to internal methods. Serialization is hand-rolled and tedious. Ensuring support for mapreduce mode is a chore because of it.

This patch refactors the tool. Options are now passed around to methods and such as a POJO instead of one-by-one. Get rid of accessors that don't help anyone. On the mapreduce side, serialization is now handled using json (jackson is a dependency anyway) instead of the hand-rolled regex we used before. Also do away with custom InputSplit and FileFormat, instead using Text and NLineInputFormat. On the local mode side, combine 1 client and N clients into the same implementation. That implementation now uses an ExecutorService, so we can later decouple number of client workers from number of client tasks. Finally, drop a bunch of confusing local state, instead use the new TestOptions POJO as a parameter to static methods.