NUnit support: Copy and Modified test to support NUnit

NUnit support: Copy and Modified test to support NUnit
-------------------------------

* NPEG.Mono.sln
-> NPEG.csproj
-> NPEG.Tests.NUnit.csproj

* NPEG.Test -> NPEG.Test.NUnit:
-> Copy & Modified tests to use NUnit:

*MSTest GUID types are not supported in MonoDevelop/Xamarin since it is tied to the VS UnitTestFramework namespace that is not available in Mono*