refs #712, improved readers

* only trigger read when network interface is available
* do not trigger all reads at same time but slightly shifted
* renamed to hasReceivedOkReply()

src/blackcore/threadedreader.h

@@ -55,6 +55,9 @@ namespace BlackCore
         //! \note override as required, default is to call initialize()
         virtual void requestReload();
 
+        //! Network available
+        bool isNetworkAvailable() const;
+
         //! Get the timer interval (ms)
         //! \threadsafe
         int interval() const;