Improve process of referencing assembly from other TapPackage.

Today (9.4) you need to:

• Add the package to your csproj using <AdditionalOpenTapPackage>
• Then build to get the package payload (including the assembly/assemblies) installed in the bin/Debug folder
• in Visual Studio, add a reference using "Browse" and point to the assembly in the bin/Debug folder

Instead we could automatically add references to all assemblies in packages added using <AdditionalOpenTapPackage>. This could be controlled by an option like<AdditionalOpenTapPackage Reference="true">