GNOME Shell integration for Chrome version 5

• Added internationalization support:
  • Added Russian translation.
  • Added German translation (contributed by @kirrmann)
• Fixed update period when browser was closed - it's recalculated now as needed.

• Disabled update check for unsupported platforms. Currently supported "linux" and "openbsd" (as reported by Chrome runtime) (contributed by @kirrmann)

• Improved error messages. Show message on https://extensions.gnome.org/ when unsupported platform is used.