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/exeggutor.asm

@@ -0,0 +1,10 @@
+; ExeggutorPokedexEntry: ; 0x1b8ff6
+	db "COCONUT@" ; species name
+	dw 607, 2650 ; height, weight
+
+	db   "Living in a good"
+	next "environment makes"
+	next "it grow lots of"
+	page "heads. A head that"
+	next "drops off becomes"
+	next "an EXEGGCUTE.@"