Added NUnit utility project to filter test cases belonging to specific c...

Added NUnit utility project to filter test cases belonging to specific category from an NUnit XML result file.

Usage - In console type:
NunitUtility.exe <NUnit XML filepath> <NUnit Test Category name> <output file path>
Checking with @lukechurch, as he maintains what goes in the project. Are you fine with tools going into the main project? This is a tool Aparajit wrote to do Nunit compares.

Otherwise, let us know where you prefer to include these in the repo