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/skiploom.asm

@@ -0,0 +1,10 @@
+; SkiploomPokedexEntry: ; 0x1cd928
+	db "COTTONWEED@" ; species name
+	dw 200, 20 ; height, weight
+
+	db   "As soon as it"
+	next "rains, it closes"
+	next "its flower and"
+	page "hides in the shade"
+	next "of a tree to avoid"
+	next "getting wet.@"