RN Android: Support View Manager Commands that are strings

Summary:
Right now JS triggers a view manager command with the following code:

```
UIManager.dispatchViewManagerCommand(
  ReactNative.findNodeHandle(this),
  UIManager.getViewManagerConfig('RCTView').Commands.hotspotUpdate,
  [destX || 0, destY || 0],
);
```

As we want to get rid of calls to UIManager, we need to stop looking for the integer defined in native from JavaScript. We will be changing methods like this to be:

```
UIManager.dispatchViewManagerCommand(
  ReactNative.findNodeHandle(this),
  'hotspotUpdate',
  [destX || 0, destY || 0],
);
```

We need to support ints and Strings to be backwards compatible, but ints will be deprecated.

Reviewed By: shergin

Differential Revision: D15955444

fbshipit-source-id: d1c488975ae03404f8f851a7035b58a90ed34163

ReactAndroid/src/main/java/com/facebook/react/uimanager/UIImplementation.java

@@ -748,6 +748,11 @@ public class UIImplementation {
     mOperationsQueue.enqueueDispatchCommand(reactTag, commandId, commandArgs);
   }
 
+  public void dispatchViewManagerCommand(int reactTag, String commandId, @Nullable ReadableArray commandArgs) {
+    assertViewExists(reactTag, "dispatchViewManagerCommand");
+    mOperationsQueue.enqueueDispatchCommand(reactTag, commandId, commandArgs);
+  }
+
   /**
    * Show a PopupMenu.
    *