Code refactoring

The code was repetitive and old. This change is one iteration towards a
complete refactoring of the code which brings it to a better state.

Also, the extension icon now can be clicked to open the options page.

Change-Id: I998355cd871e31d6590608ff2563d43040944a83
diff --git a/templates/manifest.gjson b/templates/manifest.gjson
index 5889bf3..84ba035 100644
--- a/templates/manifest.gjson
+++ b/templates/manifest.gjson
@@ -17,7 +17,10 @@
     "256": "icons/translate-256.png"
   },
   "background": {
-    "scripts": ["background.js"],
+    "scripts": [
+      "js/common.js",
+      "background.js"
+    ],
     "persistent": false
   },
   "options_page": "options.html",
@@ -25,5 +28,6 @@
     "page": "options.html",
     "chrome_style": true
   },
+  "browser_action": {},
   "default_locale": "en"
 }