Restore WhatsApp (electron#492)

This reverts commit 3ba1d77.

Author: ckerr

apps/whatsapp/whatsapp-icon.png

@@ -0,0 +1,11 @@
+name: WhatsApp
+description: 'Free IM, voice & video calls'
+website: 'https://www.whatsapp.com'
+keywords:
+    - free calls
+    - free online calls
+    - free calls on mobile
+    - messaging
+    - chat
+    - voip
+category: 'Social Networking'