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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/machop.asm

@@ -0,0 +1,10 @@
+; MachopPokedexEntry: ; 0x1b8065
+	db "SUPERPOWER@" ; species name
+	dw 207, 430 ; height, weight
+
+	db   "It trains by"
+	next "lifting rocks in"
+	next "the mountains. It"
+	page "can even pick up a"
+	next "GRAVELER with"
+	next "ease.@"