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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/qwilfish.asm

@@ -0,0 +1,10 @@
+; QwilfishPokedexEntry: ; 0x1d07b1
+	db "BALLOON@" ; species name
+	dw 108, 90 ; height, weight
+
+	db   "When faced with a"
+	next "larger opponent,"
+	next "it swallows as"
+	page "much water as it"
+	next "can to match the"
+	next "opponent's size.@"