Sample app for testing

This PR is far from being complete, but I wanted to run this through you before putting any more time on it.

Here's the idea:

* Create an *extremely* simple app to install and uninstall
* Make that app log very clear information on it's current version, and what is being executed exactly
* Run an install, an uninstall and verify
  * That the files are indeed present in the expected location
  * That the log file contains exactly what is supposed to be there
* Run an update
  * from multiple variations of the Releases directory
  * From the file system as well as an IIS mapping (including a Web.config to make it easy to setup)

So, either using xunit or just using a PowerShell script, we'll be able to test most edge cases in integration tests.

This is better than what I had to do manually, which is manually try cases with my own app.

It will also help documentation by providing a real life example people can look for when trying to understand how they should integrate.

What do you think?