customize message for no entries#47

Please add the function to customize the message, if no entries are available. Thats helpful if you use datatables in different situations

Seems like the same thing as in https://features.wpdatatables.com/139

Yes, ideally this would be individual to each table, but even if the unifersal variable was available as a hook you could write a bit of PHP to that would be better than the current situation.