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/flaaffy.asm

@@ -0,0 +1,10 @@
+; FlaaffyPokedexEntry: ; 0x1cd5b8
+	db "WOOL@" ; species name
+	dw 207, 290 ; height, weight
+
+	db   "Because of its"
+	next "rubbery, electric-"
+	next "ity-resistant"
+	page "skin, it can store"
+	next "lots of electric-"
+	next "ity in its fur.@"