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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/abra.asm

@@ -0,0 +1,10 @@
+; AbraPokedexEntry: ; 0x1830d5
+	db "PSI@" ; species name
+	dw 211, 430 ; height, weight
+
+	db   "It hypnotizes"
+	next "itself so that it"
+	next "can teleport away"
+	page "when it senses"
+	next "danger, even"
+	next "if it is asleep.@"