[Android][Extensions] W3C SysApps Contacts API

The implementation is based on 26 August 2013 editor's draft version:
http://www.w3.org/2012/sysapps/contacts-manager-api/

Including:
* Save/Update in batch and for individual contacts
* Find/List/Remove contacts
* Contact change event handler

Design ideas can be found in the ["Intent to implement" document](http://www.mail-archive.com/crosswalk-dev@lists.crosswalk-project.org/msg00346.html).
Feature: [XWALK-49](https://crosswalk-project.org/jira/browse/XWALK-49)