Merge branch 'wip/constraints'

Merge branch 'wip/constraints'

* wip/constraints: (24 commits)
  Add the Cogl API reference to the fixxref extra directories
  Document the internal MetaGroup class
  Remove the construct-only flag from ActorMeta:name
  doc: Remove gtk-doc annotations from the json-glib copy
  doc: Fix parameter documentation
  Add named modifiers for Action and Constraint
  Remove a redundant animation
  Set the stage resizable in test-constraints
  Use a 9 grid for the constraints test
  Miscellaneous documentation fixes
  docs: Document animating action and constraint properties
  docs: Document BindConstraint and AlignConstraint
  constraint: Rename BindConstraint:bind-axis
  constraints: Add AlignConstraint
  tests: Add a constraints interactive test
  constraint: Add BindConstraint
  actor: Implement Animatable
  animation: Use the new Animatable API for custom properties
  animatable: Add custom properties to Animatable
  constraint: Add ClutterConstraint base class
  ...

Conflicts:
	configure.ac