Adjust to let total soil thickness and max root depth be varied and not fixed

[MostafaGomaa93]

Description

The indices of the first 4 layers (layers close to land surface) are from 51 to 55 (as long as the total soil thickness equals 5 m). However, if we change the total soil thickness (not 5 m), then the indices of the first 4 layers will not be from 51 to 55 anymore. So, a simple change in these 3 files (one, two, three) to get the proper indices of the first 4 layers. These changes are related to issue 237.

Checklist

• [x] Add a reference to related issues.
• [x] @mentions of the person or team responsible for reviewing proposed changes.
• [x] This pull request has a descriptive title.
• [x] 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.
• [x] 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 please see my comment on the size of ModelSettings.DeltZ. Also, can you add one line to the changelog file explaining the changes? Thanks. After fixing the code, I will re-generate the exe file.

Could you show me how can I make changes in the changelog file and where is that file?

[SarahAlidoost]

@MostafaGomaa93 please see my comment on the size of ModelSettings.DeltZ. Also, can you add one line to the changelog file explaining the changes? Thanks. After fixing the code, I will re-generate the exe file.

Could you show me how can I make changes in the changelog file and where is that file?

The CHANGELOG.md is in the root of STEMMUS_SCOPE folder. In the file, under the section Unreleased/fixed, you can add one item for explaining changes in this pull request. Here example:

# Unreleased

**Changed:**

- ....

**Fixed:**

- .....
- The issue of defining te indices of first four layers.... is fixed in .... 

[MostafaGomaa93]

@MostafaGomaa93 please see my comment on the size of ModelSettings.DeltZ. Also, can you add one line to the changelog file explaining the changes? Thanks. After fixing the code, I will re-generate the exe file.

Could you show me how can I make changes in the changelog file and where is that file?

The CHANGELOG.md is in the root of STEMMUS_SCOPE folder. In the file, under the section Unreleased/fixed, you can add one item for explaining changes in this pull request. Here example:

# Unreleased

**Changed:**

- ....

**Fixed:**

- .....
- The issue of defining te indices of first four layers.... is fixed in .... 

Thanks, I did it already