Project directory selector notebook for tutorials

[tennlee]

          [OPTIONAL]

Might I suggest a selector pattern - reason: I prefer changing control paths without relying on commenting/uncommenting, it also seems like a nicer way to extend it further if needed (to me anyway).

mapping_org_to_datapath = {
    "UKMO": ...,
    "NCI": ...,
    "NIWA": ...,
}
wbench_data_dir = mapping_org_to_datapath["UKMO"]

Originally posted by @nikeethr in #73 (comment)

[nikeethr]

Also

[OPTIONAL]

Same as above, https://github.com/ACCESS-Community-Hub/PyEarthTools/pull/73/files#r2017726308

it may be worth having data sources in a single notebook such as Org_Data_Sources.ipynb or some such thing (not sure about the naming convention)

then the %run magic can be used to load it and use it. This way only one place needs to be changed if the data sources move/update.

[nikeethr]

essentially the above suggestion - any tutorial utility that should be easily modifiable (but shouldn't be hard-locked into the code), can be in a separate ipynb file which can then be loaded using %run common_useful_things.ipynb. Alternatively abstracted to a python file - but this is less accessible from jupyter notebooks.