more undo commands

- add edit command for duplicating map events
- add edit commands for painting map collision
- edit commands that delete events now select
  the proper next event

include/core/map.h

@@ -23,6 +23,7 @@
 #define BORDER_DISTANCE 7
 
 class MapPixmapItem;
+class CollisionPixmapItem;
 class BorderMetatilesPixmapItem;
 
 class Map : public QObject
@@ -97,6 +98,9 @@ public:
     MapPixmapItem *mapItem = nullptr;
     void setMapItem(MapPixmapItem *item) { mapItem = item; }
 
+    CollisionPixmapItem *collisionItem = nullptr;
+    void setCollisionItem(CollisionPixmapItem *item) { collisionItem = item; }
+
     BorderMetatilesPixmapItem *borderItem = nullptr;
     void setBorderItem(BorderMetatilesPixmapItem *item) { borderItem = item; }