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/porygon.asm

@@ -0,0 +1,10 @@
+; PorygonPokedexEntry: ; 0x1cc353
+	db "VIRTUAL@" ; species name
+	dw 207, 800 ; height, weight
+
+	db   "An artificial"
+	next "#MON created"
+	next "due to extensive"
+	page "research, it can"
+	next "perform only what"
+	next "is in its program.@"