Add monit support for emma and mia. Improve support for phoenix modules.

[benarmston]

See comment https://github.com/alces-flight/concertim-bootstrap/pull/13#issuecomment-1280662351 for description of issue and potential solution.

Useful links:

• https://www.digitalocean.com/community/tutorials/understanding-systemd-units-and-unit-files
• http://jdebp.info/FGA/linux-control-groups-are-not-jobs.html
• http://jdebp.info/FGA/systemd-house-of-horror/two-services.html
• https://alesnosek.com/blog/2016/12/04/controlling-a-multi-service-application-with-systemd/
• https://unix.stackexchange.com/questions/228277/grouping-systemd-services

Also, see the postgresql.service and postgresql@.service.