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/jumpluff.asm

@@ -0,0 +1,10 @@
+; JumpluffPokedexEntry: ; 0x1cd998
+	db "COTTONWEED@" ; species name
+	dw 207, 70 ; height, weight
+
+	db   "Even in the fierc-"
+	next "est wind, it can"
+	next "control its fluff"
+	page "to make its way to"
+	next "any place in the"
+	next "world it wants.@"