Set slacks to zero

[Andresj89]

Fixes/Addresses/Summary/Motivation:

This PR adds a method to set slacks to zero for the strategic model. The method checks if the termination condition of the solver is unfeasible, in that case the slacks are activated and the model is run again.

Changes proposed in this PR:

• The run_strategic_model.py has been simplified. It now contains call to the method solve_model(model, options) which receives a model object and a dictionary with the following options:

options = {
    "deactivate_slacks": True,
    "scale_model": True,
    "scaling_factor": 1000000,
    "running_time": 60,
    "gap": 0,
    "water_quality" True}

• I modified create_model() slightly to "attach" df_sets and df_parameters to the model object so we don't have to pass those in as part of the postprocess_water_quality_calculation(model, opt).

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[melody-shellman]

Overall looks good. I like this new restructuring of code, it is definitely cleaner. I ran the code with our four modes (capacity vs distance, input vs calculated) and all outputs looked good! Only change suggested is to remove df_parameters as an input to _preprocess_data (line 5212), similar to the other methods.

[NienkeWagenaar]

I removed two other unused imports. Other than that it looks good!

[melody-shellman]

Looks good, thanks for implementing those suggestions!

[melody-shellman]

Looks good, runs as expected.

[NienkeWagenaar]

Looks great!