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/oddish.asm

@@ -0,0 +1,10 @@
+; OddishPokedexEntry: ; 0x182836
+	db "WEED@" ; species name
+	dw 108, 120 ; height, weight
+
+	db   "During the day, it"
+	next "stays in the cold"
+	next "underground to"
+	page "avoid the sun."
+	next "It grows by bath-"
+	next "ing in moonlight.@"