Fixed problem with embedding or exporting tilesets with Wang sets

The Wang sets were not cloned completely, missing their edge and corner
colors. This would result in an invalid Wang set that would fail to load.

See http://discourse.mapeditor.org/t/tiled-fails-to-open-maps-with-embedded-tilesets/3040

src/libtiled/wangset.cpp

@@ -783,10 +783,16 @@ WangId WangSet::templateWangIdAt(unsigned n) const
 
 WangSet *WangSet::clone(Tileset *tileset) const
 {
-    WangSet *c = new WangSet(tileset, mName, mImageTileId);
+    WangSet *c = new WangSet(*this);
 
-    c->mWangIdToWangTile = mWangIdToWangTile;
-    c->mTileInfoToWangId = mTileInfoToWangId;
+    // Caller is responsible for adding the WangSet to this tileset
+    c->setTileset(tileset);
+
+    // Avoid sharing wang colors
+    for (QSharedPointer<WangColor> &wangColor : c->mEdgeColors)
+        wangColor.reset(new WangColor(*wangColor));
+    for (QSharedPointer<WangColor> &wangColor : c->mCornerColors)
+        wangColor.reset(new WangColor(*wangColor));
 
     return c;
 }