Add IAM4VP model

[jemrobinson]

Pull Request

Description

Adds the IAM4VP model (using the implementation from ocf-iam4vp).

How Has This Been Tested?

Tested on a local run.

• Yes

If your changes affect data processing, have you plotted any changes? i.e. have you done a quick sanity check?

• Yes
• n/a

Checklist:

• My code follows OCF's coding style guidelines
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings