Give nlapply an OmitFailures argument
test nlapply with OmitFailures

* all 3 variants
Don’t print error messages when OmitFailures=T/F
Give nmapply an OmitFailures argument as well
dev: add more contexts for neuronlist tests
Merge branch 'feature/nlapply-failures'

* feature/nlapply-failures:
  dev: add more contexts for neuronlist tests
  Give nmapply an OmitFailures argument as well
  Don’t print error messages when OmitFailures=T/F
  test nlapply with OmitFailures
  Give nlapply an OmitFailures argument