Add `happiness` field to `Pokemon`
Add `Display.updatePokemon()`

Kinda inefficient to create a new `Pokemon` object each time... I should
consider saving the object and using `Pokemon.prototype.changeSet()`
instead
Remove unused `value` attributes

Also correct class names for level and happiness inputs
Add `change()` handlers to most elements
Add `Pokemon.randomMoveset()`

Let's things outside the Pokemon object generate a random moveset for a
Pokemon.

Also fix `Pokemon.prototype.changeSet()`