[MapView] Support for annotation callouts, annotation press, callout presses and pin animation

Summary:
Started from here - https://github.com/facebook/react-native/issues/1120. Most functionality for annotations were missing so I started implementing and somehow got caught up until the entire thing was done.

![screen shot 2015-05-12 at 10 07 43 pm](https://cloud.githubusercontent.com/assets/688326/7588677/8479a7a4-f8f9-11e4-99a4-1dc3c7691810.png)

2 new events:
- callout presses (left / right)
- annotation presses

6 new properties for annotations:
- hasLeftCallout
- hasRightCallout
- onLeftCalloutPress
- onRightCalloutPress
- animateDrop
- id

1 new property for MapView
- onAnnotationPress

---
Now the important thing is, that I implemented all of this the way "I would do it". I am not sure this is the 'reacty' way so please let me know my mistakes 😄

The problem is that there is no real way to identify annotations which makes it difficult to distinguish which one got clicked. The idea is to pass a `id` and whether it has callouts the entire way with the annotation. I had to
Closes https://github.com/facebook/react-native/pull/1247
Github Author: David Mohl <me@dave.cx>

Test Plan: Imported from GitHub, without a `Test Plan:` line.

Libraries/Components/MapView/MapView.js

@@ -35,6 +35,34 @@ type MapRegion = {
 var MapView = React.createClass({
   mixins: [NativeMethodsMixin],
 
+  checkAnnotationIds: function (annotations: Array<Object>) {
+
+    var newAnnotations = annotations.map(function (annotation) {
+      if (!annotation.id) {
+        // TODO: add a base64 (or similar) encoder here
+        annotation.id = encodeURIComponent(JSON.stringify(annotation));
+      }
+
+      return annotation;
+    });
+
+    this.setState({
+      annotations: newAnnotations
+    });
+  },
+
+  componentWillMount: function() {
+    if (this.props.annotations) {
+      this.checkAnnotationIds(this.props.annotations);
+    }
+  },
+
+  componentWillReceiveProps: function(nextProps: Object) {
+    if (nextProps.annotations) {
+      this.checkAnnotationIds(nextProps.annotations);
+    }
+  },
+
   propTypes: {
     /**
      * Used to style and layout the `MapView`.  See `StyleSheet.js` and
@@ -84,14 +112,14 @@ var MapView = React.createClass({
 
     /**
      * The map type to be displayed.
-     * 
+     *
      * - standard: standard road map (default)
      * - satellite: satellite view
      * - hybrid: satellite view with roads and points of interest overlayed
      */
     mapType: React.PropTypes.oneOf([
-      'standard', 
-      'satellite', 
+      'standard',
+      'satellite',
       'hybrid',
     ]),
 
@@ -126,11 +154,34 @@ var MapView = React.createClass({
       latitude: React.PropTypes.number.isRequired,
       longitude: React.PropTypes.number.isRequired,
 
+      /**
+       * Whether the pin drop should be animated or not
+       */
+      animateDrop: React.PropTypes.bool,
+
       /**
        * Annotation title/subtile.
        */
       title: React.PropTypes.string,
       subtitle: React.PropTypes.string,
+
+      /**
+       * Whether the Annotation has callout buttons.
+       */
+      hasLeftCallout: React.PropTypes.bool,
+      hasRightCallout: React.PropTypes.bool,
+
+      /**
+       * Event handlers for callout buttons.
+       */
+      onLeftCalloutPress: React.PropTypes.func,
+      onRightCalloutPress: React.PropTypes.func,
+
+      /**
+       * annotation id
+       */
+      id: React.PropTypes.string
+
     })),
 
     /**
@@ -158,6 +209,11 @@ var MapView = React.createClass({
      * Callback that is called once, when the user is done moving the map.
      */
     onRegionChangeComplete: React.PropTypes.func,
+
+    /**
+     * Callback that is called once, when the user is clicked on a annotation.
+     */
+    onAnnotationPress: React.PropTypes.func,
   },
 
   _onChange: function(event: Event) {
@@ -170,8 +226,34 @@ var MapView = React.createClass({
     }
   },
 
+  _onPress: function(event: Event) {
+    if (event.nativeEvent.action === 'annotation-click') {
+      this.props.onAnnotationPress && this.props.onAnnotationPress(event.nativeEvent.annotation);
+    }
+
+    if (event.nativeEvent.action === 'callout-click') {
+      if (!this.props.annotations) {
+        return;
+      }
+
+      // Find the annotation with the id of what has been pressed
+      for (var i = 0; i < this.props.annotations.length; i++) {
+        var annotation = this.props.annotations[i];
+        if (annotation.id === event.nativeEvent.annotationId) {
+          // Pass the right function
+          if (event.nativeEvent.side === 'left') {
+            annotation.onLeftCalloutPress && annotation.onLeftCalloutPress(event.nativeEvent);
+          } else if (event.nativeEvent.side === 'right') {
+            annotation.onRightCalloutPress && annotation.onRightCalloutPress(event.nativeEvent);
+          }
+        }
+      }
+
+    }
+  },
+
   render: function() {
-    return <RCTMap {...this.props} onChange={this._onChange} />;
+    return <RCTMap {...this.props} onPress={this._onPress} onChange={this._onChange} />;
   },
 });