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/slugma.asm

@@ -0,0 +1,10 @@
+; SlugmaPokedexEntry: ; 0x1d0ab8
+	db "LAVA@" ; species name
+	dw 204, 770 ; height, weight
+
+	db   "These group to-"
+	next "gether in areas"
+	next "that are hotter"
+	page "than normal. If it"
+	next "cools off, its"
+	next "skin hardens.@"