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/chikorita.asm

@@ -0,0 +1,10 @@
+; ChikoritaPokedexEntry: ; 0x1cc988
+	db "LEAF@" ; species name
+	dw 211, 140 ; height, weight
+
+	db   "It loves to bask"
+	next "in the sunlight."
+	next "It uses the leaf"
+	page "on its head to"
+	next "seek out warm"
+	next "places.@"