[Runtime] Implement 'onInstalled' event API.

'onInstalled' event is sent to main page,
1. when the application is first installed.
2. when the application is updated to a new version.
https://crosswalk-project.org/jira/browse/XWALK-723

The PR implements the 'onInstalled' API for the first use case.
Use case 2 isn't implemented at present due to Crosswalk application
update is not supported yet.
[Runtime] Add browsertest for onInstalled event API.