Actual dex sprites for S/M and US/UM

These are the sprites which are shown in the Alola Pokédex. The sprites
we currently have in main-sprites/ are shown when you heal your pokemon
at the pokemon center. Unlike those sprites, this set only contains
sprites for the 400-ish which are actually in the pokedex; it does not
contain sprites for every pokemon. Partly for that reason, i'm leaving
the current set where they are and adding these in a new directory.

There were a few blank sprites in the dump which are not included.
They were: Totem forms in S/M, and Zygarde 10% and 50% with Power
Construct in both S/M and US/UM.