QuickInfoMargin -> FSharp.Editing

[cloudRoutine]

Dependent on completion of #1412

• Move flattener and flattenLines
• Disentangle updateAtCaretPosition into a function that takes the caret position and the current document and returns the tooltip:string option,errrors:(FSharpErrorSeverity * string list) [] and newWord: range (instead of snapshotspan)

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