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/omastar.asm

@@ -0,0 +1,10 @@
+; OmastarPokedexEntry: ; 0x1cc42e
+	db "SPIRAL@" ; species name
+	dw 303, 770 ; height, weight
+
+	db   "Its heavy shell"
+	next "allowed it to"
+	next "reach only nearby"
+	page "food. This could"
+	next "be the reason it"
+	next "is extinct.@"