Add some extra detail to the Discussion section of the
composite actor recipe, concentrating on the pros and
cons of this approach.
Also explain more about the Clutter parts of the implementation.
Also general tidy up of language and style.
Include all the code examples inline as part of the recipe.
Remove sections around each code example, as these are
unnecessary; leave full discussion for the Discussion section
instead of trying to cram it in around the code example.
Added a new recipe for creating a non-rectangular
actor using ClutterPath (aka "shaped pick") and
the Cogl primitives API.
Also cleaned up XML alignment in the actors.xml
file.
Explains how to make an actor transparent so that other actors
are visible through it.
Also explains a bit more generally about opacity and how
it's computed from the actor, container, and color; and how actor
visibility is affected by depth (fog) and depth order.
Made usage of docbook elements consistent across
recipes; to ensure the conventions are kept by others,
added a section about how to write and style recipes.
