Notebook execution model via better sectioning

[numere-bot]

DESCRIPTION

Describe, what you observe or want to be changed:
The interaction with a notebook-like execution model seems to be very appreciated by the user base of any data science software. Providing something similar may increase the acceptance level of NumeRe

Describe, what you expect to happen:
Provide a notebook-like execution model by improved code sectioning within scripts.

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DEVS' SECTION

ANALYSIS

(Describe, what's the issue and which changes have to be made)

IMPLEMENTATION STEPS

(see also our Wiki for implementation guidelines)

• Implement the necessary changes in a new branch created here on GitHub
• Test your implementation

DOCUMENTATION STEPS

(see also our Wiki for further information)

• Update the changes log
• Add comments to your implementation
• Add Doxygen documentation comments- Create or update the documentation articles (*.NHLP and *.NDB files, if needed)
• Update the language strings (*.NLNG files, if needed)

PULL REQUEST

• Create a pull request for your changes
• Fill out the template
• Assign @numere-org/maintainers as reviewers

[numeredev]

Add also markdown section headline #, ##, and ### parsing while converting to PDF.

##! # First level
##! ## Second level
##! ### Third level