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/wigglytuff.asm

@@ -0,0 +1,10 @@
+; WigglytuffPokedexEntry: ; 0x1826e9
+	db "BALLOON@" ; species name
+	dw 303, 260 ; height, weight
+
+	db   "The rich, fluffy"
+	next "fur that covers"
+	next "its body feels so"
+	page "good that anyone"
+	next "who feels it can't"
+	next "stop touching it.@"