Add some grunt scaffolding to run perf tests

Add grunt tasks to do the following:

* Inline a JS file at the end of an HTML file.
* Run an arbitrary shell command on a device (part of the sdb
  task).

Add grunt config to enable performance testing:

* Add a task to inline a JS file which saves performance.timing
  to localStorage.
* Add a task to push a localStorage dump script to the device.
* Add a task to run the localStorage dump script.
* Add a task to reinstall the app, stop/start it 10 times, then
  dump localStorage to the console.
Split index.html into two pieces

Load majority of the HTML once the initial page is show
Load majority of the HTML once the initial page is shownn
Replace background pngs with jpgs