Add new API call for "update" class to check system for updates.

Possible response arrays include

"security":{ "name":"FreeBSD System Update" }
"majorupgrade":{ "name":"Update to 10.3", "tag":"releng10.3", "version":"10.3-RELEASE" }
"patch":{ "name":"StandAlone Update", "tag":"mypatch", "details":"Updates PKG to FOO", "date":"20160120", "size":"5MB" }
"pkgupdate":{ "name":"System Package Updates" }

REST Request:
-------------------------------
PUT /sysadm/update
{
   "action" : "checkupdates"
}

REST Response:
-------------------------------
{
    "args": {
        "checkupdates": {
            "status": "noupdates"
        }
    }
}

  bSocket Request:
-------------------------------
{
   "name" : "update",
   "args" : {
      "action" : "checkupdates"
   },
   "namespace" : "sysadm",
   "id" : "fooid"
}

WebSocket Response:
-------------------------------
{
  "args": {
    "checkupdates": {
      "status": "noupdates"
    }
  },
  "id": "fooid",
  "name": "response",
  "namespace": "sysadm"
}

src/library/sysadm-update.cpp

@@ -65,6 +65,5 @@ QJsonObject Update::checkUpdates() {
 
   // Update status that we have updates
   retObject.insert("status", "updatesavailable");
-
   return retObject;
 }