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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/houndoom.asm

@@ -0,0 +1,10 @@
+; HoundoomPokedexEntry: ; 0x1d0f66
+	db "DARK@" ; species name
+	dw 407, 770 ; height, weight
+
+	db   "The pungent-"
+	next "smelling flame"
+	next "that shoots from"
+	page "its mouth results"
+	next "from toxins burn-"
+	next "ing in its body.@"