Provide/test Singularity support

[luiskuhn]

Description of feature

Feedback from peer-review:

While this pipeline was initially created using nf-core tools, which integrate support for a range of container technologies, the nf-root pipeline was designed to work specifically with Docker containers. In particular given the technical difficulties for containerizing the Fiji-based software needed to execute the RATIOCONV process, which unfortunately needs the “containerOptions” directive to work properly. We are aware that this requirement limits portability, in particular for HPC clusters, where using Docker is a security risk.

The “containerOptions” directive:

root-tissue-analysis/modules/local/ratioconv/main.nf

Line 14 in 2240abb

containerOptions "--network=none --memory-swap -1 --user root"