Start working on a simple Launcher app.

Let GButton have an optional icon (GraphicsBitmap) that gets rendered in the
middle of the button if present.

Also add GraphicsBitmap::load_from_file() which allows mmap'ed RGBA32 files.
I wrote a little program to take "raw" files from GIMP and swizzle them into
the correct byte order.

SharedGraphics/Point.h

@@ -26,6 +26,13 @@ public:
         move_by(delta.x(), delta.y());
     }
 
+    Point translated(int dx, int dy)
+    {
+        Point point = *this;
+        point.move_by(dx, dy);
+        return point;
+    }
+
     void constrain(const Rect&);
 
     bool operator==(const Point& other) const