Add singularity profile

[jennyfothergill]

nf-core/nanoclust pull request

This PR adds a singularity profile, fixes the conda profile, fixes the test db paths, and updates the container for consensus_classifciation.

PR checklist

• This comment contains a description of changes (with reason)
• If you've fixed a bug or added code that should be tested, add tests!
• If necessary, also make a PR on the nf-core/nanoclust branch on the nf-core/test-datasets repo
• Ensure the test suite passes (nextflow run . -profile test,docker). I have tested the test example using the singularity profile.
• Make sure your code lints (nf-core lint .).
• Documentation in docs is updated
• CHANGELOG.md is updated
• README.md is updated

Learn more about contributing: CONTRIBUTING.md

[jennyfothergill]

should fix #70, #77, #62, #60

[danpal96]

@jennyfothergill I have also tried to create a singularity profile but it always ends giving me this error:

BLAST Database error: No alias or index file found for nucleotide database [/tmp/db] in search path [/A2/danielpalma/projects/smk-ont-amplicon/resources/PGP-test/nf_test/NanoCLUST/work/0d/af38afc8c48e1022cc441cdcb524fb::/tmp/db/taxdb:]

Does this happen to you?