Improve PRS computation

[leonschuetz]

• [ ] allow reference base to be effect allele (required for some lifted SNPs)
  • [ ] adapt megSAP conversion script
  • [ ] adapt VcfCalculatePRS to handle this case (- [ ] check VcfCheck)
• [ ] add additional output for VcfCalculatePRS to export TSV with all found variants, allele counts...
• [ ] adapt calculate_prs_distribution.php to exclude certain disease groups

[leonschuetz]

• [ ] PGS file format not valid
  • [ ] validation of all variants where AF doesn't match