Change Boolean to Logical

[DavidSagan]

Boolean implies there are only two values (true and false) but for PALS we are using tri-state logic with the added null (formerly named: NotSet). I therefore propose changing Boolean to Logical in the documentation.

[ax3l]

Open to the rename.

More generally, we have required and optional parameters, where not all optional parameters have defaults. This can apply to numerical, string and boolean values -- so it raises the question why we want to treat bools differently then the others (or just call them bool, optional in the docs, like we would do int, optional).

For compatibility, it might be ideal if we define as many defaults as possible in PALS, to leave less open to interpretation.

[DavidSagan]

Where is there no default for an optional parameter?

[DavidSagan]

And since all types of parameters can have a default, I don't see that this is treating logicals any differently.

[ax3l]

Ah, I see. Must have misremembered.

After checking the current docs again, we only use NotSet on booleans exactly once for field_master: NotSet.
I think I need to see more examples that absolutely cannot be expressed as true/false for boolean values in a sensible manner, especially with other parameters around them (e.g., next to field_master is also an is_on).

Would we allow NotSet on any other numerical or string values, too? (like a C++ std::optional or YAML null) Need to see more examples I think.

P.S.: we changed NotSet to null for better compatibility https://pals-project.readthedocs.io/en/latest/introduction.html#syntax-used-in-this-document Need to update the field_master example.