Changed the tests to use the Api Key from appSettings, changed the Setup method Signature

Made the following changes:
1) Added a `TestHelper` class to read the api key from the appSettings
2) Changed the tests to use `TestHelper.ApiKey` to get the api key instead of defining the key in every test class
3) Changed the `Setup` method signature in the test method to remove the `TestContext` method as the VS Test runner was ignoring these tests as the signature did not match the anticipated Setup method signature.
4) Added a note for contributors to create a `appSettings.config` file with the Api Key so that the tests pass.