Removed workarounds for alias templates, variadic templates and
anonymous enums, but 1.8.2 has some bug with forward declarations
causing classes to appear in default namespace, breaking
cross-references.
It prevents unwanted implicit conversions from e.g. nullptr to Camera,
Vector2 to Physics::Point etc. By making all the constructors explicit
it is easier to routinely add the keyword to all new classes instead of
thinking about cases when to add and when not to.
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.
Vladimír Vondruš