Teach write.cmtkreg() to give a warning if versions of CMTK reg differ
Change default asp to 1 for image.im3d()
Merge pull request #116 from ajdm/im3dasp

Change default asp to 1 for image.im3d()
Merge pull request #115 from ajdm/safercmtk

Teach write.cmtkreg() to give a warning if versions of CMTK reg differ
make WithNodes=F the default for plot3d.neuronlist

* because this is what I want 99.9% of the time for neurons
* it's harmless for dotprops objects though it would be better
  style to avoid it bein passed on when irrelevant
add c.neuronlist method

* closes #117
Verbatim copy of nat functions for direct potential synapses
Add functions for approx potential synapses
new interface function potential_synapses
process neuronlists with same directionality

* the direct method is presently asymmetric
tidy up and document
Add missing function when using bounds
Add doi url for Stepanyants ref

* can’t seem to get \href to behave though
Make sure that we return 0 when inputs are missing rows
formatting
Merge branch 'feature/potential_synapses'

* first functional version using cleaned up version of Cell 2007
  paper implementation.
* clearly lots of potential for optimisation in direct method
* feature/potential_synapses:
  formatting
  Make sure that we return 0 when inputs are missing rows
  Add doi url for Stepanyants ref
  Add missing function when using bounds
  tidy up and document
  process neuronlists with same directionality
  new interface function potential_synapses
  Add functions for approx potential synapses
  Verbatim copy of nat functions for direct potential synapses
fix method signature for prune.neuronlist

* will cause trouble with export
Add db argument to plot3d.character
test for a bugs in subset.neuronlist

* processing of integer subset expressions is broken
fix bug in processing of integer subset expressions in subset.neuronlist 

* + additional tests