Have the locale ready to dispatch with INIT

[Mardak]

In #2991, we looked into having TopStoriesFeed get App.locale state, but it was clunky in having its init partially deferred. Instead ActivityStream should dispatch INIT with locale set already. Not sure if this also means ActivityStream instead of LocalizationFeed should be watching for the locale change so that the feed is specifically for updating strings..

[Mardak]

Unclear if this is still desired now that LocalizationFeed uses user preferred languages as opposed to app locale.

[Mardak]

#3920 switched us back to (negotiated) app locales

[Mardak]

Services.locale.getAppLocaleAsLangTag is simple enough to call to not need to stash in our own redux store as content won't need it anyway because the locale is part of the html.