update selector to use fixed update time step

Add a new Animation2 module that processes fixed update time steps.
The original Animation module will be removed later when all animations
use a fixed update step.
don't update selector matrix until it's necessary

This pattern will need to be added to other objects too.
update cell to use fixed update time step
remove variable time animation module
rename Animation2 module to Animation
remove unused watch references
remove watch dependency when raising the board