Rename all files in data/pokedex/entries/

Some people suggested this would be a good idea, and make management of
the files easier. I'm inclined to agree.

data/pokedex/entries/espeon.asm

@@ -0,0 +1,10 @@
+; EspeonPokedexEntry: ; 0x1d0155
+	db "SUN@" ; species name
+	dw 211, 580 ; height, weight
+
+	db   "The tip of its"
+	next "forked tail"
+	next "quivers when it is"
+	page "predicting its"
+	next "opponent's next"
+	next "move.@"