Fixed element selection in websites that were blocking it with CSP.

* New data selection UI engine. It is faster and more resilient to websites having CSS rules that break the UI.
* A new page load detection engine has been added. The new page load detection system will handle a lot of edge cases:
* immediate redirect after page load
* service workers
* hash tag changes
* quicker load when there is a slowly loading asset
* won't fail on an error page if there is an immediate redirect to a successful page
* data extraction will be retried if a redirect occurs during data extraction
* improved content type checking
* window.history.push changes

* CouchDB has been deprecated. Users that were using it will be able to continue to use it but new users won't be able to change data storage. We plan to replace the current data storage engine (PouchDB) with simpler one to reduce problems with sitemap and data storage.
* privacy policy page and an option to opt-out of extension metric gathering via options page.
* new users will see a welcome page with a quick startup guide
* reduced extensions permission requirements.
* Overall code quality improvements