Synchronize lesson contents and Jupyter notebooks

[jhlegarreta]

Lesson (instructor, teaching) contents that are pulled and rendered in the Carpentries incubator lesson website and the Jupyter notebook contents are out of sync: the latter correspond to the contents removed in PR #41, and such contents seem to be a pre-Carpentries version of the contents.

However, much of that material is relevant, and needed, as some of the current lessons (e.g. Data organization with BIDS) have little content, and/or no exercises.

Similarly, some figures that were included in the removed episodes_md Markdown files or the Jupyter notebooks are not included in the rendered materials.

Specifically:

• _episodes_md/02-anatomy-of-nifti: the BIDS JSON metada part ("In addition to metadata embedded in the NIfTI header, the (...)") needs to be recovered, and probably transferred to the Data organization with BIDS episode.
• _episodes_md/03-data-organization-bids: almost all content needs to be recovered.
• _episodes_md/04-open-mri-datasets: large parts need to be recovered: excerpts related to OpenNeuro; DataLad introduction, first commands; almost all contents in the Exploring a bids dataset and all of its exercises; all exercises using BIDSlayout.
• _episodes_md/05-bids-derivatives: some minor passages need to be recovered.

Also, solutions to the exercises need to be included in the Markdown and Jupyter files: a way to do this can be found in the SDC-BIDS-dMRI lesson.

Note that removing the _episodes_md was a necessary step to avoid errors in the transition to the Carpentries Workbench infrastructure.

[jhlegarreta]

The branch https://github.com/carpentries-incubator/SDC-BIDS-IntroMRI/tree/lunchnlearn should also be considered to see if there are contents that should be recovered.