Bug 982029 - [MMS/SMS] Display email in SMS/MMS Threads r=Julien

https://bugzilla.mozilla.org/show_bug.cgi?id=982029
we should eventually rename this, but not in this patch (because it's nearly ready and I don't want to rename things now). Can you add a comment in Utils.getPhoneDetails saying that "tels'" can actually contain emails too.