FindReferencesFilter -> FSharp.Editing

[cloudRoutine]

Dependent upon completion of Open Documents Tracker #1411

Disentangle the production of the reference list from reporting progress in getDocumentState into a function that takes the caret position and the document path as arguments

Code Located @ https://github.com/fsprojects/VisualFSharpPowerTools/blob/master/src/FSharp.Editing.VisualStudio/Symbol/FindReferencesFilter.fs