Parameter Scenario fixes

[mrvisscher]

Parameter scenario files currently give unexpected results when the default column is not supplied. This happens because parameters are not sampled based on their group-name combination but rather on their order within the file. This PR fixes this issue.

Checklist

• Keep pull requests small so they can be easily reviewed.
• Update the documentation
  • For in-code documentation, please follow the numpy style guide.
  • For user documentation, please update the wiki in
    ./activity_browser/docs/wiki
• Update tests.
• Link this PR to related issues by using closing keywords.

If you have write access (otherwise a maintainer will do this for you):

• Categorize the PR by setting a good title and adding one of the labels:
  bug, feature, ui, change, documentation, breaking, ci
  as they show up in the changelog.
• Add a milestone to the PR (and related issues, if any) for the intended release.
• Request a review from another developer.

[coveralls]

coverage: 53.298% (+0.02%) from 53.279%
when pulling 7d44823 on mrvisscher:sdf-fixes
into a1681e6 on LCA-ActivityBrowser:main.