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/ledian.asm

@@ -0,0 +1,10 @@
+; LedianPokedexEntry: ; 0x1ccfa0
+	db "FIVE STAR@" ; species name
+	dw 407, 780 ; height, weight
+
+	db   "In the daytime"
+	next "when it gets warm,"
+	next "it curls up inside"
+	page "a big leaf and"
+	next "drifts off into"
+	next "a deep slumber.@"