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] Implement 'onInstalled' event API.