Added support for accessing slave configs

* Implemented for Infinispan 5.2+, 6
* Added derived threadCount attribute to TestIteration
Hmm, I can see that I made even the other fields public - could you fix that, and use accessor method (addNormalizedSlaveConfiguation() and getNormalizedSlaveConfigurations() wrapped as Collections.unmodifiableMap())? The idea is that Report should be append-only.