add examples for Cell07PNs dataset
Add neuron code straight from AnalysisSuite
updated docs for neuron class (based on as.neuron/is.neuron)
Switch to lazy data loading

* simpler and no real penalty
Don't load data explicitly
Get neuron arithmetic working
remove duplicate as.neuron def
roxygenise for neuron arithmetic
test and fix scale.neuron
documentation/export fixes for xyzmatrix(<-)

* a method that doesn't need documenting just needs
#' @S3method method class
and nothing else
* generally shouldn't be necessary to export methods (just generic)
  in which case need @S3method in place of @export
Add kcs20 neuronlist of 20 dotprops objects

* flycircuit kenyon cells
implement dotprops objects
typos in kcs20 docs