setdiff.neuronlist second arg can be character vector
Give find.neuron an invert arg

* closes #172
Give find.soma an invert arg as well

* and simplify docs in process
Merge branch 'feature/neuroml'

* WIP for #169 but more work required to handle all types of morphml inputs
* feature/neuroml:
  test (failure) for neuroml2
  Test that we can read valid neurons from neuroml format
  Add test data from neurml.org
  fix bugs due to earlier renaming
  trap neuroml2 files
  cable information is optional in neuroml
  n(euro)ml->morphml as appropriate
  functions to convert neuroml cell(s) to nat::neuron
  add process_neuroml_cell
  rename to read.neuroml since this is all it does so far
  return cells (still as XML objects) rather than names
  ensure we identify default namespace
  first steps in importing neuroml (XML) files
Fix handling of StartPoint in find.soma

* closes #173
Simplify handling of colours when plotting points only
Fix node colours when WithAllPoints=TRUE

* closes #175
Plot end points in blue not green

* since default node colour for simple points is green when all nodes plotted
Document that WithText plots indices not PointNo
setdiff.neuronlist second arg can be character vector
Give find.neuron an invert arg

* closes #172
Give find.soma an invert arg as well

* and simplify docs in process
Fix handling of StartPoint in find.soma

* closes #173
Simplify handling of colours when plotting points only
Fix node colours when WithAllPoints=TRUE

* closes #175
Plot end points in blue not green

* since default node colour for simple points is green when all nodes plotted
Document that WithText plots indices not PointNo
Add swc format conversion of 2 neuroml v1 files

* from Neuronland converter
* will use for testing
fix col names of cabled

* when only one non-standard column
Fix - actually fetch fract_along_parent