Bug 1076706 - [Smart Screen][Home] Implement card listing and launching function

Please review only the commit of Bug 1076706, because the base (bug 1076702) has not landed yet

https://bugzilla.mozilla.org/show_bug.cgi?id=1076706
nit: I feel `SmartApp` is more weird.... well, maybe `App` was a good one. How about `Application`?