Bug 840210 - search engine must be customizable at build time

* Created new object stores for search engines and settings
* Created unit tests for new database logic
* Provided upgrade path between database versions and more intelligent first time run detection
* Allowed search engine to be customised at build time for multiple network variants
* Refactored customisation spaghetti code
* Moved helpers into utilities.js and respective tests into utilities_tests.js
* Renamed places.js to browser_db.js as it's really more than just places now
* Added default search engine and bookmarks to applications-data.js