Help text should be configurable, at the time of deployment

[martin-henz]

The current help text is very specific and hard-wired into the sources of the Source Academy:

Please use the following resources when you encounter issues with this system.

For critical technical issues that seriously affect your learning experience, email the Technical Services of the NUS School of Computing at techsvc@comp.nus.edu.sg or call 6516 2736.
For non-critical technical issues, such as enhancement suggestions, please use the issue system of the Source Academy repositories on GitHub.
For issues related to the content of missions, quests, paths and contests, use the respective forum at piazza, or approach your Avenger, Reflection instructor or lecturer.

[chownces]

Addressed by #1878