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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/ledyba.asm

@@ -0,0 +1,10 @@
+; LedybaPokedexEntry: ; 0x1ccf2c
+	db "FIVE STAR@" ; species name
+	dw 303, 240 ; height, weight
+
+	db   "It is timid and"
+	next "clusters together"
+	next "with others. The"
+	page "fluid secreted by"
+	next "its feet indicates"
+	next "its location.@"