Use the right default value for include_notebooks

[delucchi-cmu]

Change Description

This is a silly thing -

If you said "no" to include_docs, we didn't ask the question for include_notebooks. And so we don't record an answer for include_notebooks and the default answer from the copier.yml file is used in all places (which was True).

This sets the default according to the answer from the include_docs: if we're not including docs, then don't include notebooks; if we're including docs, default to also including notebooks.

Nearly all of the jinja in the rest of the template was doing the right thing, assuming you have correct values for include_docs and include_notebooks.

Closes #332

Checklist

• This PR is meant for the lincc-frameworks/python-project-template repo and not a downstream one instead.
• This change is linked to an open issue
• This change includes integration testing, or is small enough to be covered by existing tests

[drewoldag]

Looks great. Thank you!