Setting the priority rules right for Track class

Id is not set as a mandatory parameter in the constructor - it will be
populated only after insertion in the database.
AlbumId - same story, no need to have it mandatory.
Adjusting Album entity class. Defining the priorities for members.

Adding UnknownAlbum instance and correlating it to instance on the
database layer.
Fixing Fingerprint entity class, defining correct priorities for its properties

Running the tests within the transaction s.t. the database will remain
clean afterwards.
Skipping static properties for Expression builder.
Restructuring Test project

Integration and Unit tests are now separated.
Adding test execution before a package is built.

Before the package is build all unit tests will be executed. In case any
of them fails, no nuget package is going to be created.
In case of sending pull requests, run build.cmd in order to make sure
everything is working correctly.