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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/dragonair.asm

@@ -0,0 +1,10 @@
+; DragonairPokedexEntry: ; 0x1cc7dc
+	db "DRAGON@" ; species name
+	dw 1301, 360 ; height, weight
+
+	db   "It is called the"
+	next "divine #MON."
+	next "When its entire"
+	page "body brightens"
+	next "slightly, the"
+	next "weather changes.@"