Call the callbacks when redetection starts, move matrix map deletion to individual controllers to avoid attempting to delete const pointers

ResourceManager.cpp

@@ -196,8 +196,14 @@ void ResourceManager::DetectDevices()
     | we shall remove it first                          |
     \*-------------------------------------------------*/
     detection_percent = 0;
+    detection_string  = "";
+
+    DetectionProgressChanged();
+
     Cleanup();
 
+    DeviceListChanged();
+
     /*-------------------------------------------------*\
     | Start the device detection thread                 |
     \*-------------------------------------------------*/