Add UnitTest project template

[mmnosek]

Starting from 2.4, we support self-hosted mode and unit tests, finally. For now, we've started with this cookbook in documentation but I think we can make the experience better.

There is a code to repeat while setting up a unit test project. Isn't it possible to include "Starcounter Unit Test" template into our visual studio extension? Points 1-5 from the Unit Test cookbook can be definitely covered by such template. Plus, additionally, such template will immediately indicate that Starcounter supports unit tests "natively". @joozek78 also mentioned that some of this code can be tested on NuGet, not in the template. If this really makes sense, why not.

@miyconst @ubbeK @Mackiovello what do you think?

[Mackiovello]

I tried to do this right after writing the cookbook page: https://github.com/Starcounter/Starcounter.VisualStudio/commits/XUnitTemplate

If I remember correctly, I failed to add XUnit to the template.

This is a nice-to-have but far from a priority. Although, if you know how to do it, creating the template should be trivial since you basically just have to copy-paste the code.

[miyconst]

Since XUnit tests support is one of the public key features of the Odessa (2.4) release, the template has to be implemented. The only question is when and by whom.

[ubbeK]

Sounds like a good idea in order to help out with tests for Starcounter apps. The project should not be called UnitTest though since we will never know what kind of level a developer / tester will use the project at. Hence, throw out Unit and only call it Test (or with any combination of another key word like Starcounter).

[Mihaiii]

I don't know how urgent is this, but I can take it after 15.10.2018.
Is it's needed before that, please remove my assignment.