Updated trashcan functionality to use animalObjects

Trashcan will now mark the 'active' boolean variable inside of the
animalObject to false when a workingAnimal is being deleted. Animals
that are inactive are ignored during the fee generation.

Also fixed a bug where workingAnimals DOM elements were too large to be
detected as hovering over the trashcan. Changed the tolerance to "touch"
so any touching of the elements causes the Droppable to work.