692 create population counts

[Jday7879]

Pull Request Title

Creating population counts function

Summary

function to create the population count output for MBS
This can be output as dataframe or saved to output_path as an optional extra

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

Checklists

This pull request meets the following requirements:

Creator Checklist

• Installable with all dependencies recorded
• Runs without error
• Follows PEP8 and project-specific conventions
• Appropriate use of comments, for example, no descriptive comments
• Functions documented using Numpy style docstrings
• Assumptions and decisions log considered and updated if appropriate
• Unit tests have been updated to cover essential functionality for a reasonable range of inputs and conditions
• Other forms of testing such as end-to-end and user-interface testing have been considered and updated as required

If you feel some of these conditions do not apply for this pull request, please
add a comment to explain why.

Reviewer Checklist

• Test suite passes (locally as a minimum)
• Peer reviewed with review recorded

Additional Information

Please provide any additional information or context that would help the reviewer understand the changes in this pull request.

Related Issues

Link any related issues or pull requests here.

[robertswh]

Looks great. I've made a couple of suggestion for comments and I think the sampled column name needs changing to is_sampled to be consistent with all the changes I committed to this branch yesterday. Happy to merge once you've checked those suggestions.

[robertswh]

I changed this to "is_sampled" everywhere else, so I think it needs changing here

[robertswh]

Great work