Tweaks to 'Deploy on Android' page

Amendments after merging PR #101, relating to https://crosswalk-project.org/jira/browse/XWALK-1240

* Moved the explanation of shared/embedded mode to the "Run on Android" page (as you may want to use shared mode for a local deployment/testing)
* Changed the title of the page to "Deploy to Android store"
* Rewrote most of its content, referring to the "Run on Android" page for the details about shared vs. embedded.