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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/victreebel.asm

@@ -0,0 +1,10 @@
+; VictreebelPokedexEntry: ; 0x1b826e
+	db "FLYCATCHER@" ; species name
+	dw 507, 340 ; height, weight
+
+	db   "Once ingested into"
+	next "this #MON's"
+	next "body, even the"
+	page "hardest object"
+	next "will melt into"
+	next "nothing.@"