Display component methods on the website and tweak the documentation

Summary:The website now displays public methods on components. This was implemented mostly in react-docgen via #66. This adds a <Method> component that is used by the component and API doc pages to display documentation for a method.

It also adds some missing documentation and tweak some existing one to integrate with this feature. I also prefixed some component methods with an '_' so they don't show up in the doc.

**Test plan (required)**

Tested every component page locally to make sure the methods doc was displayed properly.
Tested an API page to make sure it still worked properly.
Closes https://github.com/facebook/react-native/pull/6890

Differential Revision: D3159911

Pulled By: vjeux

fb-gh-sync-id: 1e6a4640cda6794496d9844c1af6a1451c017dcc
fbshipit-source-id: 1e6a4640cda6794496d9844c1af6a1451c017dcc

Libraries/Components/DrawerAndroid/DrawerLayoutAndroid.android.js

@@ -223,7 +223,10 @@ var DrawerLayoutAndroid = React.createClass({
     }
   },
 
-  openDrawer: function() {
+  /**
+   * Opens the drawer.
+   */
+  openDrawer: function(test: number) {
     UIManager.dispatchViewManagerCommand(
       this._getDrawerLayoutHandle(),
       UIManager.AndroidDrawerLayout.Commands.openDrawer,
@@ -231,6 +234,9 @@ var DrawerLayoutAndroid = React.createClass({
     );
   },
 
+  /**
+   * Closes the drawer.
+   */
   closeDrawer: function() {
     UIManager.dispatchViewManagerCommand(
       this._getDrawerLayoutHandle(),