Have PackageSigner update dependencies to use signed version

[wilka]

I'm trying to use Signature.Core.PackageSigner to produce a strong name version of ReactiveUI, however when I produce the reactiveui.Signed package, it still depends on the unsigned reactiveui-core.

I'd like to be able to update the package dependencies so that it also depends on the signed version (in this case reactiveui-core.signed)

[maartenba]

That's currently not built in, however should be relatively easy to do by editing the .nuspec file in the package.