Dialer: Helplines: Use a webview dialog

* Instead of relying on one browser we can actually display a webview
  ourselves
* Set various headers to clear cache and to not track
* Displays a progressbar and loading text while the page loads

Co-authored-by: Michael W <baddaemon87@gmail.com>
Change-Id: Ibad2832c0cb6bcef79b5f348c40ca76c2516b295