cookbook: Added layout introduction and "stacking actors" recipe

Expanded the layout introduction and added a recipe about
stacking actors using ClutterBinLayout, with two examples.

doc/cookbook/examples/layouts-stacking-diff-sized-actors.c

@@ -0,0 +1,78 @@
+#include <clutter/clutter.h>
+
+static const ClutterColor dark_grey = { 0x66, 0x66, 0x66, 0xff };
+static const ClutterColor light_grey = { 0xcc, 0xcc, 0xcc, 0xff };
+
+int
+main (int argc, char *argv[])
+{
+  ClutterActor *stage;
+  ClutterLayoutManager *layout;
+  ClutterActor *box;
+  ClutterActor *rect1, *rect2;
+  guint align_x, align_y, diff_x, diff_y;
+
+  clutter_init (&argc, &argv);
+
+  stage = clutter_stage_get_default ();
+  clutter_actor_set_size (stage, 400, 400);
+
+  layout = clutter_bin_layout_new (CLUTTER_BIN_ALIGNMENT_START,
+                                   CLUTTER_BIN_ALIGNMENT_START);
+
+  box = clutter_box_new (layout);
+
+  rect1 = clutter_rectangle_new_with_color (&dark_grey);
+  clutter_actor_set_size (rect1, 400, 200);
+
+  rect2 = clutter_rectangle_new_with_color (&light_grey);
+  clutter_actor_set_size (rect2, 200, 400);
+
+  clutter_container_add (CLUTTER_CONTAINER (box),
+                         rect1,
+                         rect2,
+                         NULL);
+
+  /*
+   * 2 = CLUTTER_BIN_ALIGNMENT_START
+   * 3 = CLUTTER_BIN_ALIGNMENT_END
+   * 4 = CLUTTER_BIN_ALIGNMENT_CENTER
+   */
+  for (align_x = 2; align_x < 5; align_x++)
+    {
+      for (align_y = 2; align_y < 5; align_y++)
+        {
+          diff_x = align_x - 1;
+          if (align_x == 3)
+            diff_x = 3;
+          else if (align_x == 4)
+            diff_x = 2;
+
+          diff_y = align_y - 1;
+          if (align_y == 3)
+            diff_y = 3;
+          else if (align_y == 4)
+            diff_y = 2;
+
+          ClutterColor *color = clutter_color_new (255 - diff_x * 50,
+                                                   100 + diff_y * 50,
+                                                   0,
+                                                   255);
+          ClutterActor *rect = clutter_rectangle_new_with_color (color);
+          clutter_actor_set_size (rect, 100, 100);
+          clutter_bin_layout_set_alignment (CLUTTER_BIN_LAYOUT (layout),
+                                            rect,
+                                            align_x,
+                                            align_y);
+          clutter_container_add_actor (CLUTTER_CONTAINER (box), rect);
+        }
+    }
+
+  clutter_container_add_actor (CLUTTER_CONTAINER (stage), box);
+
+  clutter_actor_show (stage);
+
+  clutter_main ();
+
+  return 0;
+}