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/elekid.asm

@@ -0,0 +1,10 @@
+; ElekidPokedexEntry: ; 0x1d1398
+	db "ELECTRIC@" ; species name
+	dw 200, 520 ; height, weight
+
+	db   "It loves violent"
+	next "thunder. The space"
+	next "between its horns"
+	page "flickers bluish-"
+	next "white when it is"
+	next "charging energy.@"