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/wartortle.asm

@@ -0,0 +1,10 @@
+; WartortlePokedexEntry: ; 0x181993
+	db "TURTLE@" ; species name
+	dw 303, 500 ; height, weight
+
+	db   "Its long, furry"
+	next "tail is a symbol"
+	next "of longevity,"
+	page "making it quite"
+	next "popular among"
+	next "older people.@"