Feature Added : Fitnesse suite partitioning

[suratdas]

In Fitnesse, there is a new feature "suite partition" that was added last year. Details can be found at Fitnesse website. We use it to achieve parallel test execution with Fitnesse. This pull request implements this feature. Please see the screenshots.
Also, removed the checkbox "Is Suite" since both a test and a suite can be run only with a single responder "suite". The unit tests have been updated to ensure no functionality is broken. Also, added new tests for the added feature.

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[jaruzafa]

Thanks @suratdas the changes look good, I'll merge and they'll be included in the next release