* animation: Refactor AnimatedVariable
This commit decomposes the AnimatedVariable class into a base class
with the common attribute to all variable types and a templated derived
type containing strongly typed info on the type being animated.
Access to the typed version is perfomed using the visitor pattern. A
utility is provided to build a visitor on the fly using lambdas.
Adding a new type to be animated should just be a matter of adding the
typed in the list defined by the ANIMABLE_TYPES macro
The size of the commit is justified by the API change in the
AnimatedVariable class. No more vec(), fl() or col() method but a unified
value() method.
* animation: Remove visitor pattern
* animation: Fix coding style
* animation: Fix coding style
