Choose different infilling existing activities threshold by sub-region

[brynpickering]

What can be improved?

As discussed in #49, we may want to be stricter / looser about infilling where there are existing facilities of matching activity. E.g., sub-regions that are already close to census data in terms of number of households could be stricter than those which are still underpresented w.r.t. the census data.

Version

v0.2.0