anchor.diff:          | "G" -> Some LastLine
           | "<C-d>" -> Some HalfPageDown
           | "<C-u>" -> Some HalfPageUp
  +        | "<C-f>" -> Some PageDown
  +        | "<C-b>" -> Some PageUp
           | _ -> None
   
       let (|FindChar|_|) character =
  
positive.code:     | Nothing
      | HalfPageUp
      | HalfPageDown
      | CurrentLocation
      | Selection
      | SelectionStart
  
negative.code:             let visibleLineCount = getVisibleLineCount editor
              let halfwayDown = Math.Min(editor.Document.LineCount, editor.Caret.Line + visibleLineCount / 2)
              editor.Caret.Offset, editor.GetLine(halfwayDown).Offset
          | PageUp -> 
              let visibleLineCount = getVisibleLineCount editor
              let pageUp = Math.Max(1, editor.Caret.Line - visibleLineCount)
              editor.Caret.Offset, editor.GetLine(pageUp).Offset
          | PageDown -> 
              let visibleLineCount = getVisibleLineCount editor
              let pageDown = Math.Min(editor.Document.LineCount, editor.Caret.Line + visibleLineCount)
              editor.Caret.Offset, editor.GetLine(pageDown).Offset
          | CurrentLocation -> editor.Caret.Offset, editor.Caret.Offset+1
          | Selection -> 
              let selection = editor.Selections |> Seq.head
  