NUnit support: Copy and modified tests to use NUnit for use under Mono

I am working on a cross-platform Mono based project and am using NPEG and needed to add NUnit tests to support some regression testing of changes that I am making.

These changes do not touch NPEG at all since it works fine under Mono but does cause the test cases to be duplicated since NUnit has different test attributes than MS Test. 

- Robert/SushiHangover

NUnit support: Copy and modified tests to use NUnit for use under Mono
---
* NPEG.Mono.sln (New)
1 -> NPEG.csproj (Link to existing project)
2 -> NPEG.Tests.NUnit.csproj (New)

* NPEG.Test -> NPEG.Test.NUnit:
1 -> Copy & Modified tests to use NUnit

*MSTest GUID type are not supported in MonoDevelop/Xamarin since it is tied to the VS UnitTestFramework namespace that is not available in Mono*

Note: These NUnit tests run fine under Visual Studio and could be linked to the original VS solution, but you would still need a solution for MonoDevelop/Xamarin that does not include the MSTest type project (GUID ID = {3AC096D0-A1C2-E12C-1390-A8335801FDAB}