JsonTestAttirbute Framework Independant

[visschersm]

The current implementation of the JsonTestAttribute now works only for MSTest. We want to make this framework independant.

[visschersm]

Interfaces to use for NUnit: NUnitAttribute, ISimpleTestBuilder, IApplyToTest, IImplyFixture
https://github.com/nunit/nunit/blob/master/src/NUnitFramework/framework/Attributes/TestAttribute.cs

[visschersm]

@pjotrcasteel maybe we need to create an Matr.Utilities.NTest package?

• ..MSTest
• ..NUnit
• ..XUnit