Bluetooth: add Device events, and cleanup JS API

chrome/common/extensions/docs/templates/json/intro_tables.json

 {
   "alarms": {
     "Learn More": [
       {
         "link": "event_pages.html",
         "text": "Event Pages"
       }
     ]
   },
   "app_runtime": {
@@ skipping 20 matching lines @@
       },
       {
         "link": "https://developers.google.com/live/shows/9118010/",
         "text": "Chrome Apps Office Hours: Building Awesome Multi-window Apps"
       }
     ]
   },
   "bluetooth": {
     "Learn More": [
       {
-        "link": "app_usb.html",
-        "text": "Accessing Hardware Devices"
+        "link": "app_bluetooth.html",
+        "text": "Bluetooth Devices"
       }
     ]
   },
   "cookies": {
     "Permissions": [
       {
         "class": "code",
         "text": "\"cookies\""
       },
       {
@@ skipping 238 matching lines @@
     ]
   },
   "windows": {
     "Permissions": [
       {
         "partial": "intro_tables/windows_permissions.html"
       }
     ]
   }
 }