in readCheckScenarioConfig, don't ask user to ignore unknown columns if failing anyway

[orichters]

Purpose of this PR

• forbidden column titles are not treated as unknown anymore, as we know they are forbidden
• if any error exists (might also be a wrong scenario title or so) so that reading the config fails later, don't first ask the user to ignore unknown column titles
• fixing readCheckScenarioConfig() first asks whether to ignore settings, to then break on them #1377, see there for examples and how it looks now

Type of change

• Bug fix

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)
• Don't think fixing this inconveniences merits being included in the changelog CHANGELOG.md