Add plugin dependency info to prepare hook

This can be used to run apps without the need for platforms/ directory.
First attempt at hooking back button up to exit app.

Requires changes to cordova-android and x-walk plugin (so use master).
Currently has a bug where hitting back navigates to about:blank before
minimizing.
Fix cordova_plugins.js being deleted by "cca push" by hiding it from the asset manifest
Add missing alarms plugin to createproject.sh
Delete accidentally added CrxInstaller.js
Merge branch 'upstream' (back button & plugin dependencies hook)