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/clefable.asm

@@ -0,0 +1,10 @@
+; ClefablePokedexEntry: ; 0x182530
+	db "FAIRY@" ; species name
+	dw 403, 880 ; height, weight
+
+	db   "Said to live in"
+	next "quiet, remote"
+	next "mountains, this"
+	page "type of fairy has"
+	next "a strong aversion"
+	next "to being seen.@"