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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/slowpoke.asm

@@ -0,0 +1,10 @@
+; SlowpokePokedexEntry: ; 0x1b85d3
+	db "DOPEY@" ; species name
+	dw 311, 790 ; height, weight
+
+	db   "It is always so"
+	next "absent-minded that"
+	next "it won't react,"
+	page "even if its"
+	next "flavorful tail is"
+	next "bitten.@"