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/houndour.asm

@@ -0,0 +1,10 @@
+; HoundourPokedexEntry: ; 0x1d0eff
+	db "DARK@" ; species name
+	dw 200, 240 ; height, weight
+
+	db   "Around dawn, its"
+	next "ominous howl"
+	next "echoes through the"
+	page "area to announce"
+	next "that this is its"
+	next "territory.@"