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/larvitar.asm

@@ -0,0 +1,10 @@
+; LarvitarPokedexEntry: ; 0x1d169c
+	db "ROCK SKIN@" ; species name
+	dw 200, 1590 ; height, weight
+
+	db   "Born deep under-"
+	next "ground, this"
+	next "#MON becomes a"
+	page "pupa after eating"
+	next "enough dirt to"
+	next "make a mountain.@"