Distribute squirrel.exe as DotNet tool

[wouterroos]

Hi,

It might be of added value to distribute squirrel.exe as a DotNet tool so it can be installed on machines and used as a command line tool without having to use the contents of the NuGet package. This is especially useful for projects using the new csproj format since the packages won't be restored to the /packages folder in the solution root anymore.