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/graphics/Canvas.h

@@ -39,15 +39,19 @@ public:
 
 	struct Settings
 	{
+		int width  = 1;
+		int height = 1;
+		int layers = 1; // depth for 3D textures
 		PixelFormat format = PIXELFORMAT_NORMAL;
+		TextureType type = TEXTURE_2D;
 		float pixeldensity = 1.0f;
 		int msaa = 0;
 	};
 
-	Canvas();
+	Canvas(TextureType textype);
 	virtual ~Canvas();
 
-	virtual love::image::ImageData *newImageData(love::image::Image *module, int x, int y, int w, int h) = 0;
+	virtual love::image::ImageData *newImageData(love::image::Image *module, int slice, int x, int y, int w, int h) = 0;
 
 	virtual int getMSAA() const = 0;
 	virtual int getRequestedMSAA() const = 0;