Add rule for ALFA

• Investigate ALFA (https://github.com/biocompibens/ALFA)
  • to use for creating summaries of sample content
  • whether it makes sense to use it in combination with STAR
• Add Snakemake rule for ALFA
  • Run alfa for all the samples together and not for each of the samples separetely.
• Add tests for ALFA rule
  • create test sample table (e.g. for parts of chr21.bam) with sample info
  • create test case
  • write bash script that executes Snakemake with the relevant settings
  • add script to .gitlab-ci.yml