[Android] Implement Screen Orientation API through extension (Part 2)

Expose entry points functionality for extension on Android platform, since
screen orientation api is needed to binding to name space "window.screen",
we are using set entry point functionality to implement it like what tizen
is doing.

Add a new construct for XWalkExtension, which won't affect existing extension.
Merge pull request #1501 from yinli/screen_orientation_api

[Android] Implement Screen Orientation API through extension (Part 2)
[Runtime] Enable to update a web application from local

A web application can be updated from local when using "--install" switch
in command line, like this:
$ xwalk --install /path/to/xpk_package.xpk
If the application has been installed, WRT will try to update it.

https://crosswalk-project.org/jira/browse/XWALK-463
[Runtime] Re-factor for Install & Update methods in ApplicationService class