F# and C# addings (#189)

* F# - Binary Search

* C# - Double selection sort

* quick sort - f#

04_quicksort/f#/QuickSort/Program.fs

@@ -0,0 +1,21 @@
+// Learn more about F# at http://fsharp.org
+
+open System
+
+[<EntryPoint>]
+let main argv =
+    let numbers = [|3; 9; 10; 1; 4; 2; 6; 5; 8; 7|]
+
+    let rec quickSort(arr: int[]) =
+        if arr.Length < 2
+            then arr
+        else
+            let pivot = arr.[0]
+            let arrExcpetPivot = arr |> Seq.skip(1) |> Seq.toArray
+            let lessElements = quickSort arrExcpetPivot |> Seq.filter(fun n -> n <= pivot) |> Seq.toArray
+            let greaterElements = quickSort arrExcpetPivot |> Seq.filter(fun n -> n > pivot) |> Seq.toArray
+            
+            Seq.append (Seq.append lessElements [|pivot|]) greaterElements |> Seq.toArray
+
+    let sorted = quickSort(numbers)
+    0