SSM v.0.2: Code changes to activate Groundwater coupling

[MostafaGomaa93]

Description

The description of the changes proposed is in issue 220.

Checklist

• [✓] Add a reference to related issues -> issue 220..
• [✓] @mentions of the person for reviewing proposed changes -> @SarahAlidoost and @BSchilperoort.
• [✓] This pull request has a descriptive title.
• [✓] Code is written according to the guidelines.
• [x] The checks by MISS_HIT style checker and linter, below the pull request, are successful (green).
• [x] Documentation is available.
• [x] Add changes to the changelog file under section Unreleased.
• [✓] Model runs successfully.
• [x] Ask a meinatainer to re-generate exe file if matlab codes are changed. About how to create an exe file, see exe readme.

[MostafaGomaa93]

@MostafaGomaa93 very nice additions to the code. Thank you. After merging this pull request, the branch SSM_v.0.0.2 will be deleted.

Thanks so much @SarahAlidoost for your guidance