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/sunkern.asm

@@ -0,0 +1,10 @@
+; SunkernPokedexEntry: ; 0x1cda87
+	db "SEED@" ; species name
+	dw 100, 40 ; height, weight
+
+	db   "It is very weak."
+	next "Its only means of"
+	next "defense is to"
+	page "shake its leaves"
+	next "desperately at its"
+	next "attacker.@"