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/blissey.asm

@@ -0,0 +1,10 @@
+; BlisseyPokedexEntry: ; 0x1d14f7
+	db "HAPPINESS@" ; species name
+	dw 411, 1030 ; height, weight
+
+	db   "Biting into one"
+	next "of the delicious"
+	next "eggs that BLISSEY"
+	page "provides will make"
+	next "everyone around"
+	next "smile with joy.@"