Added target for cleaning NuGet packages that will run during a production build to ensure packages are all retrievable. Updated auto-version-generator for .nuspec to detect multiple copies of packages so old/new package mixes don't cause package generation issues.
Added target for cleaning NuGet packages that will run during a production build
to ensure packages are all retrievable. Updated auto-version-generator for
.nuspec to detect multiple copies of packages so old/new package mixes don't
cause package generation issues.

LexxFedoroff/Autofac,onovotny/Autofac,laizhan/autofac,LexxFedoroff/Autofac,neoe1984/https-github.com-autofac-Autofac,jruckert/Autofac,twsouthwick/Autofac,twsouthwick/Autofac,laizhan/autofac,twsouthwick/Autofac,laizhan/autofac,jruckert/Autofac,SeriaWei/Autofac,SeriaWei/Autofac,oconics/Autofac,twsouthwick/Autofac,pagebrooks/Autofac,zjmpds/Autofac,zmaruo/Autofac,onovotny/Autofac,pagebrooks/Autofac,liujunhua/Autofac,liujunhua/Autofac,oconics/Autofac,csantero/Autofac,laizhan/autofac,neoe1984/https-github.com-autofac-Autofac,autofac/Autofac,csantero/Autofac,twsouthwick/Autofac,lijianguang/Autofac,jango2015/Autofac