• Allow dispatching of messages with no target address information.
  This helps for service plugins like Apprise to make the configuration
  snippet more compact. Now, service configurations can omit the targets
  option altogether.
• apprise_single service: Accept omitted/empty addrs attribute.
• apprise_single service: Improve query parameter serialization.
• apprise_multi service: New plugin. Thanks, @psyciknz!
  The idea behind this variant is to publish messages to different Apprise
  plugins within a single configuration snippet, containing multiple recipients.