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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/weezing.asm

@@ -0,0 +1,10 @@
+; WeezingPokedexEntry: ; 0x1b92ec
+	db "POISON GAS@" ; species name
+	dw 311, 210 ; height, weight
+
+	db   "When it inhales"
+	next "poisonous gases"
+	next "from garbage, its"
+	page "body expands, and"
+	next "its insides smell"
+	next "much worse.@"