Cellranger 4.0.0 ref 2020 a

See merge request !70

# Conflicts:
#   workflow/main.nf
#   workflow/nextflow.config

Revert "Use base mask I1 = 8n, version 2.1.3"

See merge request !67

This reverts commit 35c57522

De containerize

See merge request !62

Update

Closes #37, #38, and #39

See merge request !61