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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/dodrio.asm

@@ -0,0 +1,10 @@
+; DodrioPokedexEntry: ; 0x1b884a
+	db "TRIPLEBIRD@" ; species name
+	dw 511, 1880 ; height, weight
+
+	db   "An enemy that"
+	next "takes its eyes off"
+	next "any of the three"
+	page "heads--even for a"
+	next "second--will get"
+	next "pecked severely.@"