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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/hoothoot.asm

@@ -0,0 +1,10 @@
+; HoothootPokedexEntry: ; 0x1cce58
+	db "OWL@" ; species name
+	dw 204, 470 ; height, weight
+
+	db   "It begins to hoot"
+	next "at the same time"
+	next "every day. Some"
+	page "trainers use them"
+	next "in place of"
+	next "clocks.@"