Add ability to save tileset changes

src/core/metatile.cpp

@@ -7,6 +7,17 @@ Metatile::Metatile()
     tiles = new QList<Tile>;
 }
 
+Metatile* Metatile::copy() {
+    Metatile *copy = new Metatile;
+    copy->behavior = this->behavior;
+    copy->layerType = this->layerType;
+    copy->tiles = new QList<Tile>;
+    for (Tile tile : *this->tiles) {
+        copy->tiles->append(tile);
+    }
+    return copy;
+}
+
 int Metatile::getBlockIndex(int index) {
     if (index < Project::getNumMetatilesPrimary()) {
         return index;