GNOME Shell integration for Chrome version 8

Changes

• Added Mozilla Firefox support (Firefox addons site). Native host connector version 8 or newer required.

• Added support for asynchronous browser API to extensions.gnome.org and switched chrome-gnome-shell to using such API. Review pages are works well now when browser extension is enabled.

• Moved update check code to native connector to be able to get verbose error messages when update check is failed. Python Requests 2 required now.
• Implemented notifications support in native connector. This will unify notifications for all supported browsers. As part of this change native connector rewritten as GApplication with DBus activation. DBus support is required now.
• Code cleanup.

Translations

• Czech (Marek Černocký)
• Dutch (Hannie Dumoleyn)
• French (Alexandre Franke)
• Italian (Gianvito Cavasoli)
• Polish (Piotr Drąg)
• Portuguese (Brazil) (Rafael Fontenelle)
• Spanish (Daniel Mustieles)
• Swedish (Anders Jonsson, Josef Andersson)
• Turkish (Muhammet Kara)

Known issues

• Native host connector is not working in Google Chrome and Opera when installed via Debian Stretch or Sid repositories. To know "why?" look here, here and here. For a workaround look here.

• Web extension is broken on FreeBSD because of bug 212925.