Adding unit test project

No unit tests yet
Injecting depepndency into AdRotatorComponent as interface

* Added IFileHelpers  interface
* Passing in IFileHelpers interface into AdRotatorComponent as
dependency to make mocking later easier
Adding a unit test to the project

- Added Moq to the solution to use as mocking library in the unit test
project
- Made IFileHelpers public so that Moq could use it for unit tests
- Added a unit test testing the constructor of AdRotatorComponent (to
have one passing test :) )