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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/skarmory.asm

@@ -0,0 +1,10 @@
+; SkarmoryPokedexEntry: ; 0x1d0e8c
+	db "ARMOR BIRD@" ; species name
+	dw 507, 1110 ; height, weight
+
+	db   "The feathers that"
+	next "it sheds are very"
+	next "sharp. It is said"
+	page "that people once"
+	next "used the feathers"
+	next "as swords.@"