add validateScenarios to output scripts

[pweigmann]

Purpose of this PR

This PR adds an output script to allow using piamValidation functions like validateScenarios() or validationReport directly from a REMIND directory.

Selecting the comparison option of Rscript output.R now offers validateScenarios. The number of runs to choose is not restricted, however the heatmap plots will likely have layout problems when a high number of scenarios is selected.
Currently, the only output that is generated is an .html report with interactive traffic-light heatmaps based on the validationConfig that is selected. In the future, other output options will be made available.

Type of change

• New feature
• This change requires a documentation update

Checklist:

• My code follows the coding etiquette
• I performed a self-review of my own code
• I explained my changes within the PR, particularly in hard-to-understand areas
• I checked that the in-code documentation is up-to-date
• All automated model tests pass (FAIL 0 in the output of make test)

Further information (optional):

• Test runs are here: /p/tmp/pascalwe/remind_vs

[LaviniaBaumstark]

what is a high number of scenarios?

[pweigmann]

what is a high number of scenarios?

depends a bit on the number of regions/years/models - hard to give an estimate, maybe more than 6?