Give xform.neuronlist the option to xform all points in one go

[jefferis]

This would be nice e.g. for xforming points with the nat.h5reg rJava interface which would be much quicker like this.

The problem is what happens when there are additional vertices like connectors that would not be picked up by xyzmatrix. Perhaps we need some argument to tell xyzmatrix to handle all vertices.