Add Tool Bar to Editor Mode

* Toolbar has icon buttons for the Pencil Tool, Line Tool, Rect Tool,
  Actor Tool and Link Tool.
* Remove the tab buttons from the top of the Palette window. The palette
  tab is now toggled between Swatches and Doodads by the tool selected
  on the tool bar, instead of the tab buttons setting the tool.
* Remove the "Link Doodads" button from the Doodad Palette. The Link
  Tool has its own dedicated toolbar button with the others.

image.go

@@ -41,6 +41,13 @@ func NewImage(c Image) *Image {
 	return w
 }
 
+// ImageFromTexture creates an Image from a texture.
+func ImageFromTexture(tex render.Texturer) *Image {
+	return &Image{
+		texture: tex,
+	}
+}
+
 // OpenImage initializes an Image with a given file name.
 //
 // The file extension is important and should be a supported ImageType.