ensure that nlapply (and therefore xform etc) produce identical output with neuronlistfh

* just a matter of looking after classes
test equivalence of neuronlist(fh) arithmetic
Merge branch 'feature/neuronlistfh'

* feature/neuronlistfh:
  test equivalence of neuronlist(fh) arithmetic
  ensure that nlapply (and therefore xform etc) produce identical output with neuronlistfh