Feature: watch all projects with the package installed

[Mr-Badger]

This PR is solves #57 more elegantly than the solution I presented in the issue. With this solution it's possible to watch multiple projects, or a single referenced project (no need install package into the startup project). The solution should work without breaking current functionality.

I had problems testing this with the sample projects so I couldn't add a new sample. (Tested this locally within another project.)

There are few things that need to be considered such as how configuration will be handled in referenced projects and other things I probably missed.