Lint for pipeline nf-test contents

[adamrtalbot]

Description of feature

The pipeline level nf-test should contain the following lines:

• Check that params.outdir = $outputDir:

params {
    outdir = "$outputDir"
}

• Check the versions file is valid and fits our methodology. We currently use a lib function to remove the Nextflow version but any method that checks for a valid versions.yml with the correct data would be acceptable.