docs: Add effects chapter, with introduction and first recipe

Add an effects chapter which gives a broad overview of
the abstract classes in the effects API, plus a short
example of how to apply one of the stock Clutter
effects (ClutterColorizeEffect).

The recipe explains how to create a custom ClutterDeformEffect
to produce a page fold (code based on ClutterPageTurnEffect).

The example code includes the effect class plus a small
application to apply it to a texture.

doc/cookbook/examples/effects-built-in.c

@@ -0,0 +1,58 @@
+#include <clutter/clutter.h>
+
+int
+main (int   argc,
+      char *argv[])
+{
+  ClutterActor *stage;
+  ClutterActor *texture;
+  ClutterConstraint *constraint_x;
+  ClutterConstraint *constraint_y;
+  ClutterColor *pink;
+  ClutterEffect *effect;
+  gchar *filename;
+
+  if (argc < 2)
+    {
+      g_print ("Usage: %s <path to image file>\n", argv[0]);
+      return 1;
+    }
+
+  filename = argv[1];
+
+  clutter_init (&argc, &argv);
+
+  stage = clutter_stage_new ();
+  clutter_actor_set_size (stage, 400, 400);
+  g_signal_connect (stage, "destroy", G_CALLBACK (clutter_main_quit), NULL);
+
+  texture = clutter_texture_new ();
+  clutter_texture_set_keep_aspect_ratio (CLUTTER_TEXTURE (texture), TRUE);
+  clutter_actor_set_width (texture, 300);
+
+  /* NB ignoring missing file errors here for brevity */
+  clutter_texture_set_from_file (CLUTTER_TEXTURE (texture),
+                                 filename,
+                                 NULL);
+
+  /* align the texture on the x and y axes */
+  constraint_x = clutter_align_constraint_new (stage, CLUTTER_ALIGN_X_AXIS, 0.5);
+  constraint_y = clutter_align_constraint_new (stage, CLUTTER_ALIGN_Y_AXIS, 0.5);
+  clutter_actor_add_constraint (texture, constraint_x);
+  clutter_actor_add_constraint (texture, constraint_y);
+
+  /* create a colorize effect with pink tint */
+  pink = clutter_color_new (230, 187, 210, 255);
+  effect = clutter_colorize_effect_new (pink);
+
+  /* apply the effect to the texture */
+  clutter_actor_add_effect (texture, effect);
+
+  clutter_container_add_actor (CLUTTER_CONTAINER (stage), texture);
+
+  clutter_actor_show (stage);
+
+  clutter_main ();
+
+  return 0;
+}