Made consecutive edits to map properties merge together

Like already happens for the properties of most other data types.

The new properties view made it extra noticeable that each change became
its own undo command.

src/libtiled/map.h

@@ -78,8 +78,7 @@ class TILEDSHARED_EXPORT Map : public Object
     QString exportFormat;
 
     enum Property {
-        TileWidthProperty,
-        TileHeightProperty,
+        TileSizeProperty,
         InfiniteProperty,
         HexSideLengthProperty,
         StaggerAxisProperty,
@@ -212,6 +211,7 @@ class TILEDSHARED_EXPORT Map : public Object
     void setTileHeight(int height);
 
     QSize tileSize() const;
+    void setTileSize(QSize size);
 
     bool infinite() const;
     void setInfinite(bool infinite);
@@ -455,6 +455,12 @@ inline QSize Map::tileSize() const
     return QSize(mParameters.tileWidth, mParameters.tileHeight);
 }
 
+inline void Map::setTileSize(QSize size)
+{
+    mParameters.tileWidth = size.width();
+    mParameters.tileHeight = size.height();
+}
+
 inline bool Map::infinite() const
 {
     return mParameters.infinite;

src/tiled/changelayer.cpp

@@ -23,7 +23,6 @@
 #include "changeevents.h"
 #include "document.h"
 #include "layer.h"
-#include "map.h"
 
 #include <QCoreApplication>