86 nonlinear heating curve

[FWuellhorst]

Closes #86 and fixes a minor bug introduced in #82

[ebc-aixlib-bot]

Errors in regression test. Compare the results on the following page\n https://rwth-ebc.github.io/BESMod/86_nonlinearHeatingCurve/charts

[ebc-aixlib-bot]

Thank you for making a Pull Request to BESMod!

Our CI pipeline will help you finalize your contribution.
Here's what is typically checked:

• HTML syntax of your models, primarily in your documentation.
• Adherence to the naming convention in all changed files.
• Ability to check all models.
• Ability to simulate all models, if they are examples.
• If your contribution changes existing reference results.

If HTML errors occur, I will fix the issues using a separate pull request.
For the other checks, I will post the results here: https://rwth-ebc.github.io/BESMod/86_nonlinearHeatingCurve/index.html

Tips to fix possible naming violations:

• Stick to the naming guidelines, e.g. Namespace Requirements
• Do all paramaters, variables, models, etc. have a description?
• Use absolute paths to classes! -> BESMod.Fluid.HeatExchangers.Radiator - Avoid: HeatExchangers.Radiator

If all CI stages pass and you have addressed possible naming violations, please consider the following:

• Use "group" and "tab" annotations to achieve a good visualization window.
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• Instantiate the replaceable medium package as:
  replaceable package Medium = Modelica.Media.Interfaces.PartialMedium "Medium model";
  instead of using a full media model like BESMod.Media.Water directly.
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• Stick to 80 characters per line, as long as it makes sense.
• Add or modify examples for new or revised models.
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  How? Follow the documentation here: https://github.com/ibpsa/modelica-ibpsa/wiki/Unit-Tests#how-to-include-models-as-part-of-the-unit-tests
  Tip: To create the initial script, you can use Dymolas script generator, explained here: https://www.claytex.com/tech-blog/how-to-use-a-plot-script/)

Once you have addressed these points, you can assign a reviewer.
Although this process may seem tedious, ensuring CI passes allows the reviewer to focus
their time on the actual modeling rather than syntax and unintended breakages caused by your changes.

If you have any questions or issues, please tag a library developer.
Once again, thank you for your valuable contribution!

[ebc-aixlib-bot]

Errors in regression test. Compare the results on the following page\n https://rwth-ebc.github.io/BESMod/86_nonlinearHeatingCurve/charts