Add min max to post processing script

[Benjamin Went (MetBenjaminWent)]

Description

To effectively assess runtime properties of an application using Vernier, we need to have access to the self min and the max times of a caliper.
I've updated the new class based post-processing script with this functionality, which I believe to be a baseline feature, as opposed to an optional feature uses can add with their own scripts outside of Vernier.

The python testing has been updated as required by the script.

Linked issues

Closes #238

Type of change

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How has this been tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• New tests have been added
• Tests have been modified to accommodate this change

Checklist:

• My code follows the style guidelines of this project
• 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, for both debug and optimised builds