GUI: more more more work

error dialog boxes and drawOrders improvements

src/engine/engine.h

@@ -89,6 +89,7 @@ class DivEngine {
   std::mutex isBusy;
   String configPath;
   String configFile;
+  String lastError;
 
   short vibTable[64];
 
@@ -260,6 +261,9 @@ class DivEngine {
     // change system
     void changeSystem(DivSystem which);
 
+    // get last error
+    String getLastError();
+
     // init dispatch
     void initDispatch();