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/aipom.asm

@@ -0,0 +1,10 @@
+; AipomPokedexEntry: ; 0x1cda11
+	db "LONG TAIL@" ; species name
+	dw 207, 250 ; height, weight
+
+	db   "It uses its tail"
+	next "to hang on to tree"
+	next "branches. It uses"
+	page "its momentum to"
+	next "swing from one"
+	next "branch to another.@"