AtomsBase + ACEpotentials tutorial

[cortner]

not yet ready, needs updates registered in other packages too. But looks promising so far.

[cortner]

@wcwitt -- this is ready for a first look.

To try out the workflow for the tutorial on Monday, this should be really straightforward I hope.

1. create a new folder
2. Start julia, in that folder julia --project=.
3. install ACEpotentials, then copy the tutorials

using Pkg 
Pkg.Registry.add(RegistrySpec(url="https://github.com/ACEsuit/ACEregistry"))
Pkg.add("ACEpotentials")
using ACEpotentials 
ACEpotentials.copy_tutorial()

4. Start jupyter in the local folder either from shell, or

using IJulia
IJulia.notebook(; dir = pwd())

5. Open one of the tutorials and go.