Update in help file template

[rpitonak]

• More detailed help file, helps user to better understand how to use image.
• ENVIROMENT VARIABLES heading to specify how to run the image in different ways without the need of rebuilding image.

Example help file for Perl s2i image: https://raw.githubusercontent.com/container-images/perl/master/root/help.md

[rpitonak]

Updated, please have another look.