add tutorials

[federicazanca]

closes #144
adding tutorials for PSDI Town Hall.

• Setting up janus as a code (assumes that the profile and computer are already set up, but I also did put some example config files in the folder)
• Single point (just the simple calculation)
• Geometry optimisation, and than I run singlepoint calc on all the steps and plot the energy and provenance graph.
• High-throughput screening single point calculation for the mofs in the folder structures. Showing the aiida groups, the config file and some other things I didn't use in the other tutorials
• There is nothing on MD and training/fine-tuning yet. Md works basically just like geometry or singlepoint, so it could be substituted in any of these and more or less work (with the right inputs).
  Training and fine tuning should be added at some point I guess.