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/magby.asm

@@ -0,0 +1,10 @@
+; MagbyPokedexEntry: ; 0x1d140e
+	db "LIVE COAL@" ; species name
+	dw 204, 470 ; height, weight
+
+	db   "It naturally spits"
+	next "an 1100-degree"
+	next "flame. It is said"
+	page "when many appear,"
+	next "it heralds a"
+	next "volcanic eruption.@"