Add phone-pad keyboard

Summary:
With the numeric keyboard now being an actual numeric keyboard (before
it was actually phone-pad), we need a proper phone-pad keyboard as well.

public

Reviewed By: dmmiller

Differential Revision: D2830707

fb-gh-sync-id: 80a1d314eac730e691de73a31342c014a2fa5ba6

Examples/UIExplorer/TextInputExample.android.js

@@ -242,6 +242,7 @@ exports.examples = [
         'default',
         'email-address',
         'numeric',
+        'phone-pad',
       ];
       var examples = keyboardTypes.map((type) => {
         return (