In the event someone wants to move the obj/ folder, MSBuild will not be able to locate dotnet-watch's generated targets. dotnet-watch cannot automatically find the obj folder (#244), so this command line switch allows users to point dotnet-watch to the right location.
Fixes#252 - help output shown twice in dotnet-watch
Fixes#250 - add dotnet-watch --list. Prints a list of all files discovered
Fixes#249 - better error message when GenerateWatchList fails