Extensions that use public Shell API are expected to work for all
stable 3.0 releases, so we skip setting the minor version. (This
means that they'll work in 3.0.0 and 3.0.1 without rebuilding).
Notably absent are auto-move-windows and windowsNavigator, that
hook deep into Shell code and could be broken by next minor release.
GNOME Shell emits a warning when "url" is absent in metadata.json,
adding it costs nothing. Links to the GIT repository because I
found no better page to reference.
Introduce a translation domain, gnome-shell-extensions, and use it
in extensions that have user-facing strings, instead of abusing
of translations provided by gnome-shell.
Also includes an example translation for italian, and bump the
required version for xrandr-indicator.
Depends on GNOME bug 621017.
