Buildscript and side-by-side tests.

Yes, this is my take on a simple nant-based build script. It enables you to build the solution on both windows and linux systems. Available targets:

* package = restores nuget packages.
* clean = cleans workspace.
* compile = yes, it compiles.
* test = oh yet, it runs the tests.
* build = clean, compile, test _(default)_

Although @ahelmberger did the effort to split tests from the implementation, I now drop in my take, which is to leave the tests side-by-side to their beloved implementations and let the build script strip out the tests if compiling with `configuration=release`.

Thanks for your thoughtfulness!