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
Comms app use this `entryPoint` to distinguish real app entry point because there are three app reside in comms app, though we don't really need comms app in smart-screen. However I am not sure if it is OK to remove this field. I'll remove `entryPoint` if you think it is no needed.