Drafting and refining the project guidelines

[rodet]

Let's try to improve the project overall guidelines so contributors can better plan and assess ongoing contributions.

1. The minimum size but not excessively minimalistic. I.e. only implement features that will be needed by 80% of the projects.
2. Overly document each piece of code that is not 100% clear to all users. Think of it as a course as much as a template.
3. Every time there is logic we need to write tests for it.
4. Keep the documentation up to date.