This notebook should inject a link to the actual ADF output webpage into the
jupyter book

cleaned up a couple files that were triggering pre-commit fails

hide input and output for imports, and input for cell that will eventually have
plots as output

Notebook was linking to adf_root before updating the value from config.yml;
config.yml should set the default to where we expect ADF to write webpage
(which is in the same directory tree that CUPiD writes webpage)

instead of

adf_run: True
adf_vars: ['...', '...']

Introduced

external_tool:
  tool_name: 'ADF'
  vars: ['...', '...']

I also moved this out of parameter_group since it's not needed by the
link_to_ADF.ipynb notebook (and added plotting_scripts: ['...', '...'] as an
extra option to set in config.yml)

ADF will write output to ${CUPiD}/examples/{example}/ADF_output; if
external_tool == "ADF" then that directory will be copied into _build/html/ADF