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/magcargo.asm

@@ -0,0 +1,10 @@
+; MagcargoPokedexEntry: ; 0x1d0b21
+	db "LAVA@" ; species name
+	dw 207, 1210 ; height, weight
+
+	db   "Its body is as hot"
+	next "as lava and is"
+	next "always billowing."
+	page "Flames will"
+	next "occasionally burst"
+	next "from its shell.@"