[REF] Unit tests' namespace

[pjanck]

File which is being refactored All visual unit tests + their base classes + helpers.

Looking at the compiled doxymentation, all visual unit tests are missing their namespace.

Tasks

• [ ] Introduce a new namespace UnitTesting within the OIP namespace:

    namespace OpenInfraPlatform {
    namespace UnitTesting {
    ... }}
  

• [ ] Prepare a namespace.h with defines, similar to other projects.

• [ ] Update all visual unit tests.