refs #568, improved validation and handling

* invalid models can be highlighted on stash
* selection mode can be toggled between single/multi selection (where applicable)
* color for highlighting can be set
* finetuning of menus

src/blackmisc/simulation/aircraftmodellist.cpp

@@ -176,6 +176,12 @@ namespace BlackMisc
         }
 
         CStatusMessageList CAircraftModelList::validateForPublishing() const
+        {
+            CAircraftModelList invalidModels;
+            return validateForPublishing(invalidModels);
+        }
+
+        CStatusMessageList CAircraftModelList::validateForPublishing(CAircraftModelList &invalidModels) const
         {
             if (this->isEmpty()) { return CStatusMessageList(); }
             CStatusMessageList msgs;
@@ -198,6 +204,7 @@ namespace BlackMisc
                     singleMsg.prependMessage(model.getModelString() + ": ");
                 }
                 msgs.push_back(singleMsg);
+                invalidModels.push_back(model);
             }
             return msgs;
         }