Change packaging structure of SmartStore library project

Summary of Changes:

* Added a new level in packaging (```smartstore```), since the latest Android SDK doesn't permit usage of multiple library projects with the same name if one of them has a different package.
* Modified ```config.xml``` to reflect the new path to the Salesforce plugins.
* Change package name in ```AndroidManifest.xml```.
* Reorganized imports in tests and sample apps.
* Changed visibility on one method to make it accessible to tests.