Cleaning up redundant functions

[blue442]

There are a few different ways to access data objects (e.g. agents) that provide different return types - in the /respository/db_respository.py file, there is a get_households() function that returns a list of Any, while the GeoModel object from /abm/geom_model.py has a class function get_households that looks to return a pandas dataframe.

We should figure out which approach is appropriate and get rid of the duplication. Note that there are other instances of this as well. We should expect these functions to be internally consistent with each other.