Add tests which use Castle Windsor as IoC container

[marco-bertschi]

As discussed in #19

[marco-bertschi]

I've had a quick first look at this issue, as mentioned on XUnit's Github Issue 1908 they do not support Theory on a fixture level.
There are two feasible workarounds mentioned there, one with running the tests multiple times within the build pipeline, or creating a Theory for each test. Both aren't optimal, but we should settle for either we want to have in order to test multiple IoC containers with our library. we should opt for NUnit instead, as that would give us the desired features. NUnit is also more aimed at the type of integration testing we primarily need than XUnit.

@pascalberger, @Speeedy01 Opinions?