Improve goto decl

Not for merge, just for discussion and help. 
#556

In this PR, navigating to an external type (`System.String`) works. You are taken to the correct type in object browser, without error message. But I can't get members to work properly (`System.String.Copy`) 

Anyone have a clue why it doesn't work? I'm not sure what NRefactory wants here to be able to find the member. Please check the diff and help!
In not near a computer until tomorrow, is it because that's not an fsharp entity for members etc?

> On 29 Jun 2014, at 23:50, Robert Jeppesen <notifications@github.com> wrote:
> 
> In monodevelop/MonoDevelop.FSharpBinding/Services/NRefactory.fs:
> 
> >             
> >             // Create a resolution context for the resolved type definition.
> > -           let nsp = match fsEntity.Namespace with None -> "" | Some n -> n
> > -           let unresolvedTypeDef = DefaultUnresolvedTypeDefinition (nsp, Region=region, Name=lastIdent, Accessibility=access (* , UnresolvedFile=unresolvedFile *) )
> > -
> > +           let unresolvedTypeDef = DefaultUnresolvedTypeDefinition (fsEntity.FullName, Region=region, Accessibility=access, UnresolvedFile=unresolvedFile)
> @7sharp9 Assembly name and location could be off, but the real fix is here: the overload of DefaultUnresolvedTypeDefinition that is used expects a full type name. There is another overload where you supply namespace and name separately. So we were supplying namespace as a full type name.
> 
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