Upgrade roadmap to newest versions of nf-core template

[luiskuhn]

Feedback from peer-review:

• Fix warning: WARN: Access to undefined parameter 'enable_conda' -- Initialise it to a default value eg. 'params.enable_conda = some_value'
• Include input validation using the nf-validation plugin to replace SAMPLESHEET_CHECK:
  

  root-tissue-analysis/modules/local/samplesheet_check.nf

  Line 6 in b8c6876

  process SAMPLESHEET_CHECK {

• Update to the newest versions of the nf-core template (https://nf-co.re/docs/tutorials/nextflow_training/creating_with_nf-core)