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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/staryu.asm

@@ -0,0 +1,10 @@
+; StaryuPokedexEntry: ; 0x1b9702
+	db "STARSHAPE@" ; species name
+	dw 207, 760 ; height, weight
+
+	db   "When the stars"
+	next "twinkle at night,"
+	next "it floats up from"
+	page "the sea floor, and"
+	next "its body's center"
+	next "core flickers.@"