1. Ability to configure variables from a JSON file.
2. By default, checkin.sh does not know the value of checkin_file, this commit fixes that.
3. I want to create a web interface, front end, for this project and it is easier for the PHP server to parse the json data.
• Codes have been simplified and optimized.
• E-Mail contents were assigned to variables. (For more language support)
• Description lines should be made more easily understandable.