Add internal generic_magic_check function

* since this is a pattern that is used repeatedly
refactor is.amiramesh/is.vaa3draw with generic_magic_check
fix bug in generic_magic_check for multiple files

* and add test for this
Merge branch 'master' into feature/neuroml

* master:
  fix bug in generic_magic_check for multiple files
  refactor is.amiramesh/is.vaa3draw with generic_magic_check
  Add internal generic_magic_check function
  swallow warnings in test
  avoid partial arg match to keep check happy
  path should _end_ in zip
  Move zip archive write logic to write.neurons and document
  Move zip archive reading logic to read.neurons and document
  Teach write.neuron to write multiple neurons to a zip file
  Teach read.neuron to handle a zip archive of multiple neurons
  getformatreader return list includes name of format
  Document that WithText plots indices not PointNo
  Plot end points in blue not green
  Fix node colours when WithAllPoints=TRUE
  Simplify handling of colours when plotting points only
  Fix handling of StartPoint in find.soma
  Give find.soma an invert arg as well
  Give find.neuron an invert arg
  setdiff.neuronlist second arg can be character vector
Add is.neuroml to check if file is NeuroML

* implements a number of heuristics to be as fast as possible
autodetect neuroml format files
add test for read.neuron recognising neuroml
Merge branch 'feature/neuroml'

* feature/neuroml:
  add test for read.neuron recognising neuroml
  autodetect neuroml format files
  Add is.neuroml to check if file is NeuroML