Redid all shop images.

Reworked all shop images to always be 2x2 pixel blocks (2/3rds the
original size), never scaled unevenly.

Also went through and touched up every image if needed, removing
transparent pixels for the hand on each weapon, removing arm outlines
from armors that don't cover the arm, and so on.
Moved mystery_201402 items to their own event folder; made events with few items not have their own shop folder.
Updated shop images for mystery_201403 items.
Merge pull request #184 from PeterHatch/redo-shop-images

Redid all shop images.