This change makes a small handful of improvements to our trophies,

covering the implementation of TrophyType subclasses, the presentation

of trophies, and the look of our standard trophies.
On an implementation level, TrophyType subclasses no longer need to

override __init__, as the metadata for the trophy is now stored in class

attributes. Older subclasses can install provide these through the

constructor, but will get deprecation warnings.
Trophy registration is now based on a standard registry. The existing

methods remain for compatibility, but will show deprecation warnings.
All methods and attributes are now properly documented as well.
On a presentational level, rendering problems with showing multiple

trophies or when there's an unknown trophy have been fixed. Trophies are

also no longer bound to a specific width and height (previously, this

would result in some weird problems with the positioning of the trophy).
Trophies can also provide multiple images for different resolution

levels, allowing for @2x, @3x, etc. trophy images.
The default trophies (fish and sparkly) have been updated with slightly

improved (crisper) visuals and support for Retina images. The sparkly

trophy is now more sparkly, and the fish trophy has a better base and

eye.

Unit tests pass.
Tested that trophies are still properly being calculated and assigned.
Tested that unregistered trophies previously assigned to a review request

no longer breaks the trophy banner.
Tested that multiple trophies renders correctly.
Tested that new-style and legacy trophy subclasses work.
Tested the new trophy images on Retina and non-Retina displays.