Improve nuget packages

[pauldeen79]

Maybe it would be a good idea to generate a .csproj file on the fly, calling dotnet build to generate an assembly and all nuget references in a temporary directory. This way, we don't have to store assemblies in the temp folder, and this also fixes resolving assemblies from nuget packages. (do we need "lib", or which target framework do we need?)

Edit: Maybe it would be a better option to use assembly templates. You can do whatever you want, just copy all the package binaries to the output directory and use that as probing path. (is already performed when you use the file name of the assembly)