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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/dragonite.asm

@@ -0,0 +1,10 @@
+; DragonitePokedexEntry: ; 0x1cc843
+	db "DRAGON@" ; species name
+	dw 703, 4630 ; height, weight
+
+	db   "It is said that"
+	next "somewhere in the"
+	next "ocean lies an"
+	page "island where these"
+	next "gather. Only they"
+	next "live there.@"