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/meganium.asm

@@ -0,0 +1,10 @@
+; MeganiumPokedexEntry: ; 0x1cca54
+	db "HERB@" ; species name
+	dw 511, 2220 ; height, weight
+
+	db   "Anyone who stands"
+	next "beside it becomes"
+	next "refreshed, just as"
+	page "if they were"
+	next "relaxing in a"
+	next "sunny forest.@"