Allow slicing sprite into a grid
Add sample for animations
Calculate elapsed time and call update function
Create animation class and make the sprite_node animatable
Creating interface for slicing and remove sprite class
Rename sprite_node to sprite and move it to it's one file
Add default constructor to animation
Keep consistent state of sprite during animation
Add a custom slicer
Do not copy the animation inside the sprite
Set scaling of sprite instead of setting the size directly

Setting the size directly doesn't make much sense, as it depends on the
animation.
Put origin of the sprite to the center, instead of top left
Merge branch 'Animation'