Improved mailer plugin & email by category

Now, JEM can send email notification to several case, in function of  action (new event, update event, delete event, new venue, update venue) and select type user (owner event, user group, email category, distribution list of plugin):

user group: The users of the group associated with the category of the event.
email category: A mailing list can be assigned to the category to notify new events to a category. In the future this parameter will select list of emails or name from the list of Acymailing (plugin).
It can notify to registered users of changes in the event (any update, include move to trash (delete).