C#: Add partial properties and indexers examples.

csharp/ql/test/library-tests/partial/Partial.cs

@@ -3,12 +3,30 @@ partial class TwoPartClass
     partial void PartialMethodWithBody1();
     partial void PartialMethodWithoutBody1();
     public void Method2() { }
+    // Declaring declaration.
+    public partial object PartialProperty1 { get; set; }
+    // Declaring declaration.
+    public partial object this[int index] { get; set; }
 }
 
 partial class TwoPartClass
 {
     partial void PartialMethodWithBody1() { }
     public void Method3() { }
+    private object _backingField;
+    // Implementation declaration.
+    public partial object PartialProperty1
+    {
+        get { return _backingField; }
+        set { _backingField = value; }
+    }
+    private object[] _backingArray;
+    // Implmentation declaration.
+    public partial object this[int index]
+    {
+        get { return _backingArray[index]; }
+        set { _backingArray[index] = value; }
+    }
 }
 
 partial class OnePartPartialClass
@@ -20,4 +38,10 @@ partial class OnePartPartialClass
 class NonPartialClass
 {
     public void Method5() { }
-}
+    public object Property { get; set; }
+    public object this[int index]
+    {
+        get { return null; }
+        set { }
+    }
+}