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

Move some data into a pokemon/ subdirectory

data/pokemon/dex_entries/jolteon.asm

@@ -0,0 +1,10 @@
+; JolteonPokedexEntry: ; 0x1cc28b
+	db "LIGHTNING@" ; species name
+	dw 207, 540 ; height, weight
+
+	db   "The negatively"
+	next "charged ions"
+	next "generated in its"
+	page "fur create a"
+	next "constant sparking"
+	next "noise.@"