Devoncarew run

Adding a 'Run' button. The button listens for resource focus changes and updates its enablement appropriately. Some hacking around polymer issues. A follow-up CL will have a configurable framework for launching things. Chrome app launches or Dart web app launches could then be added to that framework.

![screen shot 2014-01-15 at 9 30 46 am](https://f.cloud.github.com/assets/1269969/1922738/cda8d226-7e0a-11e3-8f15-85813d2a1492.png)

@gaurave