Docs: Create a Comprehensive User Guide

[RHammond2]

This PR adds a comprehensive user guide to ensure users for the terminal-based and code-based have all the information they need in one place to get started with running the model. In addition to documentation and docstring updates, several modifications are made for user convenience and bug fixing in the LandBOSSERunner interface.

Type of change

What types of change is it?
Select the appropriate type(s) that describe this PR

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Checklist

Put an x in the boxes that apply.

• I have run existing tests which pass locally with my changes
• I have added new tests or examples that prove my fix is effective or that my feature works
• I have added necessary documentation