Remove 'native data' and 'native units' (#331)

Resolves #331 (closed)

Somehow resolves #850 (closed)

GUI/Model/Project/LinkInstrumentManager.cpp

@@ -98,13 +98,6 @@ bool LinkInstrumentManager::canLinkDataToInstrument(const DatafileItem* realItem
         return false;
     }
 
-    /*
-    if (realItem->rank() == 1 && !realItem->hasNativeData()) {
-        ::warn(parent, "Cannot link, data is empty.");
-        return false;
-    }
-    */
-
     if (instrumentItem->alignedWith(realItem))
         return true;