Net billing updates for credit expiry and same-month usage

[berg-michael]

Description

Add UI items and default values for changes to Net Billing re: SSC Pull 1200.

I'm not familiar with the SAM project as I have only used the detailed residential PV modeling functionality. So, it's not clear to me if there is a way to determine all models that require an update to the default settings for this change. I only updated the defaults file for the Flat Plate PV Residential Model. I have also updated the relevant UI files for Utility Rate. As far as I can tell, that is sufficient to update the UI across all models, but again, I've only updated the component of SAM I have any familiarity with.

Fixes # SSC Pull 1200

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

• This change requires a documentation update

• This change modifies variables in existing compute modules. Please see Checking for PySAM Incompatible API Changes.

Checklist:

If you have added a new compute module in a SSC pull request related to this one, be sure to check the Process Requirements.

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings