Allows to animate objects, pause, repeat and resume the animations. The
user implements animation step and can perform actions on state changes.
Each Animable is part of some group which is optimized for case when no
animation is running, thus it is possible to create multiple independent
"animation islands" to improve performance.
* Camera is now templated also on underlying floating-point type.
* Drawable objects can be split into groups (e.g. for separated
rendering of transparent objects)
* Added (long time missing) test for draw() function.
Functionality present in Object is now split into three main components:
* Object itself, handling parent/children relationships
* Transformation implementation and interfaces for common functionality
* Object features, providing transformation caching and base for
cameras, collision shapes, rigid bodies etc.
Some functionality depending on former implementation is temporarily
disabled and will be reworked later.
Vladimír Vondruš