Allow scenario aliases in compareScenarios2

[simonkrogmann]

Purpose of this PR

If compareScenarios2 is started with runs that are based on the same scenario (e.g. default), they will have almost the same name in the resulting pdf (default.1, default.2), which makes comparing difficult. Now users are prompted for aliases if there are identical scenario names. For scripting backwards compatibility this only happens if the runs are selected manually. piamPlotComparison already offers a corresponding feature so no change is necessary there.

Other comparison modules may also make use of these aliases, but I have neither implemented not tested them, because I don't know which modules are still in use.

Please give lots of feedback, also about R conventions and functions, I'm learning it at the moment.

Type of change

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Parts concerned

• ◻️ GAMS Code
• ☑️ R-scripts
• ☑️ Documentation (GAMS incode documentation, comments, tutorials)
• ◻️ Input data / CES parameters
• ◻️ Tests, CI/CD (continuous integration/deployment)
• ◻️ Configuration (switches in main.gms, default.cfg, and scenario_config*.csv files)
• ◻️ Other (please give a description)

Impact

• ◻️ Bug fix
• ◻️ Refactoring
• ☑️ New feature
• ◻️ Change of parameter values or input data (including CES parameters)
• ◻️ Minor change (default scenarios show only small differences)
• ◻️ Fundamental change of results of default scenarios

Checklist

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In the end all checkboxes must be ticked before you can merge.

• I executed the automated model tests (make test) after my final commit and all tests pass (FAIL 0)
• I adjusted the reporting in remind2 if and where it was needed
• I adjusted the madrat packages (mrremind and other packages involved) for input data generation if and where it was needed
• My code follows the coding etiquette
• I explained my changes within the PR, particularly in hard-to-understand areas
• I checked that the in-code documentation is up-to-date
• I adjusted forbiddenColumnNames in readCheckScenarioConfig.R in case the PR leads to deprecated switches
• I updated the CHANGELOG.md correctly (added, changed, fixed, removed, input data/calibration)

Further information (optional)

[fbenke-pik]

Please use autoindent do make sure this is indented correctly.