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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/ninetales.asm

@@ -0,0 +1,10 @@
+; NinetalesPokedexEntry: ; 0x18260c
+	db "FOX@" ; species name
+	dw 307, 440 ; height, weight
+
+	db   "It is said to live"
+	next "a thousand years,"
+	next "and each of its"
+	page "tails is loaded"
+	next "with supernatural"
+	next "powers.@"