Expanded MQTT capabilities and much more

• The system no longer exits when configuration errors prevent startup. This leaves the container in
  a running state so it is possible to open a terminal window to the container to inspect
  things like volume mount points for missing configuration files. Resolves issue 164.
• Telegram trigger handlers now support an optional caption property to specify the text sent
  as the caption for the photo that fired the trigger. This supports mustache templates so the
  caption can be something like {{name}}: {{formattedPredictions}}. Resolves issue 154.
• MQTT trigger handlers now support an array of messages to send instead of a single message, allowing
  for different format messages to different services. For example one message could be formatted
  in a way that works for Home Assistant use and another could be formatted to trigger BlueIris recording.
  This is an optional, more advanced, way to specify MQTT triggers. The previous, simple, single topic
  method still works and is recommended for most use cases. See the wiki
  for an example of the new format. Resolves issue 153.
• A payload property is now supported on MQTT handler message configuration, along with support for
  mustache templates in the payload. This makes it possible to send a precicely formatted
  message to BlueIris that will trigger recording for a specific camera instead of having
  to use webRequest handlers. Resolves issue 151.
• Mustache templates are now supported in the webRequest handler URIs. One way to use this is
  to send additional data to BlueIris with the details of predictions that caused the trigger to fire,
  for example "http://localhost:81/admin?trigger&camera=Dog&memo={{formattedPredictions}}.
  See the wiki for
  details on available mustache variables. Resolves issue 148.
• The MQTT overall configuration now supports specifing a topic for status messages.
  Right now the only status message sent is a LWT message for when the system goes
  offline. Resolves issue 145.
• Logging level is now controlled by a VERBOSE environment variable. When set to true
  additional logging is shown in the console. When false or omitted only startup and
  successful detection messages are shown. Resolves issue 143.