Import Animation classes from juego.js

Imported Animation classes from juego.js (with the required.js stuff
removed).
Add pickup and dropoff location images

Added pickup and dropoff location sprite strips.  Created pickupLocation
and dropoffLocation animatedImages and animations.  Added
AnimationRunner objects to Dropoff and Package classes and had these
classes draw the animations in their draw method.
Move enum definitions into separate file
Get package width/heigh from animation

Get the Package width/height from the
animation.image.frameHeight/frameWidth.
Create generic DeliveryLocation class

The old Package and Dropoff classes were basically the same thing.  Join
them into a single generic DeliveryLocation class and use the enum
LOCATIONS to specify whether it's a pickup or a dropoff location.
Give the Courier better handling

Give the Courier better handling by increasing its maxTurnSpeed.
Fix bug in snapToGrid

If the coordinate given to snapToGrid is negative, it will mess up
and return a negative value, which is never what we want.
Change usage of dropoffExpireSeconds to deliveryExpirationSeconds.
Added a scoreboard

Added a scoreboard to the bottom of the screen.
Added a score multiplier

Added a score multiplier to the scoreboard.  It is doubled every set
number of successful deliveries, and it resets when a pickup or dropoff
location is missed.
Clean up functions and globals

Moved the collision function into its own collision.js file.

Moved global variable definitions into globals.js.  Got rid of those
nasty courierWidth, courierHeight, and bounds* variables.