first complete draft of `Jupyter book`

[PeerHerholz]

This PR introduces the first complete draft of the Jupyter book including multiple crucial aspects and corresponding changes. In more details, this entails the following:

• adaptation of repo structure to follow jupyter book outline

  • content and jupyter notebooks were moved to a dedicated directory called paper
  • the top-level directory now contains general/setup files including License, Readme.md, requirements.txt and such related to the computational environment
  • renaming of jupyter notebooks

• addition and adaptation of files related to the computational environment

  • requirements.txt was updated to reflect more packages and precise versions thereof
  • generate_image.sh was added and constitutes a bash script which utilizes neurodocker to create the Dockerfile necessary to rebuild the computational environment
  • Dockerfile was added and constitutes the Dockerfile creaed by generate_image.sh

[adelavega]

• Can we call the directory something other than paper? It just gives the impression that it builds the actual preprint
• We should add a link to the preprint and author names to the frontpage once it posts
• We can probably remove the Singularity image probably. It's not nearly computationally expensive enough to warrant it. Instead, we might want to highlight local installation w/ requirements.txt

Otherwise, LGTM!