set configuration variables for continuous integration

[feiloo]

PR checklist

• [ ] This comment contains a description of changes (with reason).
• [ ] If you've fixed a bug or added code that should be tested, add tests!
• [ ] If you've added a new tool - have you followed the pipeline conventions in the contribution docs
• [ ] Make sure your code lints (nf-core lint).
• [ ] Ensure the test suite passes (nextflow run . -profile test,docker --outdir <OUTDIR>).
• [ ] Usage Documentation in docs/usage.md is updated.
• [ ] Output Documentation in docs/output.md is updated.
• [ ] CHANGELOG.md is updated.
• [ ] README.md is updated (including new tool citations and authors/contributors).

Changes

add a test_ukb.config to enable ci testing on a ukb testserver. additionally set some needed configuration variables

[sci-kai]

The CI test seems to work great. Before merging, we should add some documentation about the test dataset in the README.md. This should include: Sample, size (no of variants), assay/kit, workflow with version for creating VCF files, type (here: tumor-only sequencing).

[biolancer]

After discussion on the 31th august, this PR remains on hold.