Implement DOM screen.lockOrientation and screen.unlockOrientation

Can be tested manually with http://jsbin.com/IJapIVE/4
Merge pull request #1365 from shaochangbin/app-extension-namespace

[Runtime] Move application runtime& event extension under xwalk::application namespace.
Merge pull request #1367 from kenchris/lockOrientation

Implement DOM screen.lockOrientation and screen.unlockOrientation
[Runtime] Add install_time field in ApplicationData

The time of application installing should be stored in ApplicationData
as application meta data. It is a constant, so just have a getter method
for it.
Merge pull request #1359 from takethathe/installed_time

[Runtime] Add install_time field in ApplicationData
[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.