Allow modification of settings under Config

[pharring]

Right now, you cannot get a writable settings store for the Config scope. That's hard-coded in the IVsSettingsManager implementation.

Assuming we can find the registry root, can we synthesize one over the registry APIs?

[pharring]

You can find the registry root via ILocalRegistry4. A quick test shows that the location is writable, but modifications aren't persisted. Requires more investigation.

[pharring]

Also, Microsoft.VisualStudio.Shell.VSRegistry (from MPF) has static a RegistryRoot method.