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/kangaskhan.asm

@@ -0,0 +1,10 @@
+; KangaskhanPokedexEntry: ; 0x1b94f6
+	db "PARENT@" ; species name
+	dw 703, 1760 ; height, weight
+
+	db   "To avoid"
+	next "crushing the"
+	next "baby it carries in"
+	page "its pouch, it"
+	next "always sleeps"
+	next "standing up.@"