Removing of another <*stream> #include leads to more compilation time
saving, now from ~5:12 to ~4:55. Another compilation time improvements
will now be possible only by using Clang's modules, I don't know where
to optimize further (except for getting rid of <sstream> in tests).
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