Pushover support, detection annotations, and numerous other little improvements.

• The length of time it takes to analyze an image is now calculated and available via the analysisDurationMs property in the default MQTT message. It is also available as a mustache template variable and shown in verbose logging messages. Resolves issue 242.
• MQTT messages now include the trigger's name in the name property. Resolves issue 243.
• Pushover is now supported as a trigger handler. See the wiki for how to enable it and how to configure it on a trigger. Resolves issue 232.
• Annotated images that show the objects and confidence percentage for things that fired the triggers are now available for Telegram messages. To enable the annotated image in Telegram messages set the new annotateImage property to true on the handler configuration. The annotated images are also exposed via a web server on port 4242 using their original file name for use by external services, for example http://localhost:4242/Dog_20200523-075000.jpg. By default the images are kept for 60 minutes before being deleted. This new capability comes with a performance impact due to the additional image manipulation required and is off by default. To enable it set the ENABLE_ANNOTATIONS environment variable on the trigger Docker container to true. Resolves issue 187.
• Resolve a warning when using Telegram triggers. Resolves issue 174.
• Added a new CHOKIDAR_AWAITWRITEFINISH environment variable that, when true,
  resolves issues with images getting saved to a network share that's then mounted
  to Docker as the image source. As this has a performance impact it is off
  by default. Resolves issue 236.
• An optional /node-deepstackai-trigger mount point exists for future use. Resolves
  issue 191.