Main method to refine in clients to update game logic and `sprites`

Property definitions

	# Main method to refine in clients to update game logic and `sprites`
	fun update(dt: Float) do end

lib/gamnit/flat/flat_core.nit:386,2--387,29

	redef fun update(dt)
	do
		super
		update_from_head_tracker
	end

lib/gamnit/depth/cardboard.nit:89,2--93,4