* Fix DOCS.md example configuration with custom message from file
* Move .test.message to a better named file
* Add support for additional, custom extra vars to be used in the message template
* Add cmdline/envvars to support the extra vars
* Enhance DOCS.md with example configuration using generic template file with custom vars
* Add testcase for custom template vars
* Add support for external message loaded from the file specified in Config.MessageFile
* Enable the message file option in command line/env vars
* Update docs
* Add a testcase
* Fix YAML tag in DOCS.md from 'messageFile' to 'message_file', as is commonly used in Drone
* Remove unintended blank line
* Move .test.message file to tests/ folder
