Adding framework assemblies from GAC

Description

This is a feature request. I searched the docs and the open issues and I am fairly certain this is not existing and not a duplicate.

What I want is to be able to repair my project file by deleting all of the project references and the entire bin folder, then run Paket and have all the dependencies put back correctly.

If I do this right now I lose dependencies on .Net Framework assemblies because not many NuGet packages define these, and anyway my application code might need something that none of the NuGet packages needs.

My suggestion is to extend the syntax of the paket.dependencies file to include a gac keyword at the start of the line, so my paket.dependencies might be

framework: net40
source https://nuget.org/api/v2
nuget NUnit
gac System
gac System.Data
gac System.Xml

Then in my paket.references I could put

NUnit
System
Syatem.Data
System.Xml

Start by reviewing Paket's handling of paket.dependencies and paket.references, then determine how .NET Framework assemblies from the GAC would fit the existing dependency workflow. Done means the proposed gac entries can restore the listed framework assemblies after project references and bin are removed, with appropriate validation for the syntax and references.