BHoM_Engine_Tests: Add a test project for every engine project

#### Definition of the test :

As requested by @IsakNaslundBh, and discussed with @al-fisher:
add a Test project in the BHoM_Engine_Tests for every project in the BHoM_Engine.

The reasoning is that then people just need to go and add tests, rather than have to add test projects themselves, and this should reduce possible risks.