improve quality of existing unit tests

[jsc86]

The naming of the unit tests is currently inconsistent and subpar.
This should be consolidated and any resulting strategy (naming, test patterns etc.) should be documented in the wiki.

1. assess current state of unit tests in the jsc.commons projects
2. research established unit test conventions with a focus on c#/.net/NUnit
3. make an informed decision which strategy/convention fits the jsc.commons projects best and document it in the wiki
4. consolidate/improve the existing unit tests