[Package] Implementation of Tizen Package API

This branch includes a fully functional implementation of Tizen Package API. 

API specification can be found at:
https://developer.tizen.org/dev-guide/2.2.0/org.tizen.web.device.apireference/tizen/package.html

BUG=XWALK-443
```
var info = (pkg_id.value === "current app") ?
        tizen.package.getPackageInfo() :
        tizen.package.getPackageInfo(pkg_id.value);
```