Rename all files in data/pokedex/entries/

Some people suggested this would be a good idea, and make management of
the files easier. I'm inclined to agree.

data/pokedex/entries/snubbull.asm

@@ -0,0 +1,10 @@
+; SnubbullPokedexEntry: ; 0x1d06e0
+	db "FAIRY@" ; species name
+	dw 200, 170 ; height, weight
+
+	db   "In truth, it is a"
+	next "cowardly #MON."
+	next "It growls eagerly"
+	page "in order to hide"
+	next "its fear from its"
+	next "opponent.@"