add prop_terms

[topepo]

For changes in the important package.

[hfrick]

dials already has mtry_prop(), predictor_prop(), sample_prop(), and validation_set_prop(). Can you rename this parameter to terms_prop()? I think the more distinguishing part of the name should come first.

[topepo]

It's ordered it that way because it is an analog to the existing arguments in recipes such as num_terms. It's inconsistent with the ones you mentioned, but would be consistent with its direct analogs.

[hfrick]

Then I'd like to rename all the num_*() parameters we have 😂