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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/kangaskhan.asm

@@ -0,0 +1,10 @@
+; KangaskhanPokedexEntry: ; 0x1b94f6
+	db "PARENT@" ; species name
+	dw 703, 1760 ; height, weight
+
+	db   "To avoid"
+	next "crushing the"
+	next "baby it carries in"
+	page "its pouch, it"
+	next "always sleeps"
+	next "standing up.@"