Add share button to /mybadges page that shows share modal.
Because badge thumbnails were turned into an include, internal
blocks can't be overridden where we were doing it before,
so there's some extra redirection to get around that.
Hook up Mozilla Backpack button to do modaless push
Don't show share button if underage
Commenting out additional share buttons until they're implemented
Merge pull request #602 from stenington/592-backpack-push

Push to backpack