Implement Array, Cubemap, and Volume texture types (issue #1111).

- Add love.graphics.newArrayImage, newCubeImage, and newVolumeImage.
- Add love.graphics.newCanvas(w, h, layers) and newCanvas(w, h, layers, settings). Add ‘type’ field to the settings table of newCanvas.

- Add new love.graphics.setCanvas variants: setCanvas(canvas, slice), and setCanvas(canvastable) where canvastable is in the format: {{canvas1, layer=2}, {canvas2, face=5}}

- Add Texture:getTextureType, getDepth, getLayerCount, getMipmapCount, and getFormat.

- Remove Image:getData and Image:refresh.
- Add Image:replacePixels(imagedata [, slice] [, mipmap]).

- Update Canvas:newImageData to accept a slice argument.

- Add love.image.newCubeFaces(imagedata).

--HG--
branch : minor

src/modules/image/Image.h

@@ -90,6 +90,12 @@ public:
 	 **/
 	virtual bool isCompressed(love::filesystem::FileData *data) = 0;
 
+	std::vector<StrongRef<ImageData>> newCubeFaces(ImageData *layoutData);
+
+private:
+
+	ImageData *newPastedImageData(ImageData *src, int sx, int sy, int w, int h);
+
 }; // Image
 
 } // image