Update NUnit to the new version

[lmalenfant]

The latest NUnit library has breaking changes, in Order to update to the latest package we will need to fix the breaking changes.

There are 2 options for fixing:

1. Change the code to match the new unit test Assert format,.
2. Add the alias in the csproj file to use the classic method.

The preferred method is to change the code but there are possibly hundreds of lines of code to change so we need to evaluate the code to see if this can be accomplished easily all at once.