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/cleffa.asm

@@ -0,0 +1,10 @@
+; CleffaPokedexEntry: ; 0x1cd2bc
+	db "STARSHAPE@" ; species name
+	dw 100, 70 ; height, weight
+
+	db   "If the impact site"
+	next "of a meteorite is"
+	next "found, this"
+	page "#MON is certain"
+	next "to be within the"
+	next "immediate area.@"