Please, merge my PowerShell examples for all chapters (#106)

* PowerShell 01_introduction_to_algorithms example

* PowerShell 02_selection_sort example

* PowerShell 03_recursion examples

* PowerShell 04_quicksort examples

* PowerShell 05_hash_tables examples

* PowerShell 06_breadth-first_search example

* PowerShell 07_dijkstras_algorithm example

* PowerShell 08_greedy_algorithms example

* Powershell 09_dynamic_programming example

03_recursion/PowerShell/01_countdown.ps1

@@ -0,0 +1,17 @@
+function Write-GRKCountdown
+{
+    param ($i)
+    # base case
+    if ($i -le 0)
+    {
+        return 0
+    }
+    # recursive case
+    else
+    {
+        write-Host($i)
+        return Write-GRKCountdown($i-1)
+    }
+}
+
+Write-GRKCountdown 5

03_recursion/PowerShell/02_greet.ps1

@@ -0,0 +1,21 @@
+function Write-GRKGreet2
+{
+    param ($name)
+    Write-Host("how are you, " + $name + "?")
+}
+
+function Write-GRKBye
+{
+    Write-Host "ok bye!"
+}
+
+function Write-GRKGreet
+{
+    param($name)
+    Write-Host("hello, " + $name + "!")
+    Write-GRKGreet2 $name
+    Write-Host "getting ready to say bye..."
+    Write-GRKBye
+}
+
+Write-GRKGreet adit

03_recursion/PowerShell/03_factorial.ps1

@@ -0,0 +1,14 @@
+function Get-GRKFact
+{
+    param ($x)
+    if ($x -eq 1)
+    {
+        return 1
+    }
+    else
+    {
+        return $x * (Get-GRKFact ($x-1))
+    }
+}
+
+Get-GRKFact 5