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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/parasect.asm

@@ -0,0 +1,10 @@
+; ParasectPokedexEntry: ; 0x1829e2
+	db "MUSHROOM@" ; species name
+	dw 303, 650 ; height, weight
+
+	db   "When nothing's"
+	next "left to extract"
+	next "from the bug, the"
+	page "mushrooms on its"
+	next "back leave spores"
+	next "on the bug's egg.@"