Split items/ and trainers/ into their data/ and engine/ components

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/vaporeon.asm

@@ -0,0 +1,10 @@
+; VaporeonPokedexEntry: ; 0x1cc224
+	db "BUBBLE JET@" ; species name
+	dw 303, 640 ; height, weight
+
+	db   "As it uses the"
+	next "fins on the tip"
+	next "of its tail to"
+	page "swim, it blends"
+	next "with the water"
+	next "perfectly.@"