Adding classes for scalability.
The scalability test suites can be run by invoking scalability as the run mode.
Changes summarized:
1. Any scalability suite can be added by implementing the ScalabilitySuite interface.
2. ScalabilityAbstractSuite is an abstract implementation which can be used to extend custom scalability suites.
Any implementation needs to implements 2 methods - addBenchmarks() and executeBenchmarks().
3. The actual benchmarks to be run within a suite should be implementations of the ScalabilityBenchmark.