Add a Couple of Tests

[sathukorale]

As with anything Xamarin, there is no proper way to do this. I am thinking about putting some tests into the example code itself. Press some button, it'll run the tests, and will print out the test results on a table.

Couple of test scenarios.

• Download a regular file. Check the checksum
• Start downloading a file. Stop the download while its been downloaded, and then resume again. Check the checksum.
• Start downloading multiple different files onto different directories and make sure the different directories are created, the files were downloaded and that the checksums match.
• Download the same file multiple times. Downloaded file count should correct. And the file names should be altered (some index as the suffix) to accommodate multiple instances of the same file.