integrate Python notebooks into standard documentation of Tribler

[synctext]

Besides #4521 and #4656.
We have several .ipynb files

• Trustchain sim tutorial
  • https://github.com/grimadas/BlockchainEngineering/blob/master/00_Overview.ipynb
  • https://github.com/grimadas/BlockchainEngineering/blob/master/02_Services.ipynb
• incremental-pagerank
• from ctc-executioner wiki
  • https://github.com/backender/ctc-executioner/blob/master/notebooks/order_execution_behaviour.ipynb
  • https://github.com/backender/ctc-executioner/blob/master/notebooks/order_execution_behaviour_artificial.ipynb
  • https://github.com/backender/ctc-executioner/blob/master/notebooks/orderbook_features.ipynb

[grimadas]

This is no longer relevant, as Tribler is a system not an algorithm.