Metadata of a tutorial in the same Markdown file as the tutorial

[bebatut]

As discussed during BOF at GCC/BOSC 2018 (see #941), it would be nice to have metadata of a tutorial in the same Markdown file as the tutorial to simplify the contribution.

[bebatut]

We discussed it with @erasche and came to the conclusion that we could first move some of the metadata specific to the tutorials or slides to the top metadata of the tutorial: questions, objectives, time_estimation, key_points, zenodo_link

Hopefully, the others metadata will not be touched too often and could stay in the metadata.yaml at least for now

@shiltemann what do you think?

[shiltemann]

I think this makes a lot of sense 👍

[bebatut]

We will need to update the TeSS scrapper (https://github.com/ElixirTeSS/TeSS_scrapers/blob/master/app/scrapers/galaxy_scraper.rb)