Added Markdown support; Fixed duplicated init_ functions.

[janpfeifer]

• Added DisplayMarkdown and UpdateMarkdown.
• Changed %help to use markdown.
• init_* functions:
  • Fixed duplicate rendering.
  • Added section about it in tutorial.ipynb
• Updated tutorial to used %rm to remove no longer wanted definitions.

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This discussion was created from the release Added Markdown support; Fixed duplicated `init_` functions..