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/ho_oh.asm

@@ -0,0 +1,10 @@
+; HoOhPokedexEntry: ; 0x1d185d
+	db "RAINBOW@" ; species name
+	dw 1206, 4390 ; height, weight
+
+	db   "It will reveal"
+	next "itself before a"
+	next "pure-hearted"
+	page "trainer by shining"
+	next "its bright rain-"
+	next "bow-colored wings.@"