Add scroll parameter to reindex. Closes #3253 (#3289)

Author: Stuart Cam

src/CodeGeneration/ApiGenerator/RestSpecification/Core/reindex.patch.json

@@ -0,0 +1,12 @@
+{
+  "reindex": {
+    "url": {
+      "params": {
+        "scroll": {
+          "type" : "time",
+          "description" : "Specify how long a consistent view of the index should be maintained for scrolled search"
+        }
+      }
+    }
+  }
+}