move xyzmatrix methods to xform
Change grep call to supply one pattern when multiple regions are specified
Add xyzmatrix methods for hxsurf class

* and tests
* this allows surface objects to xformed and mirrored
teach mirror function to accept numeric axis specification

* 1-indexed
* + tests
xformpoints can cope with gregxform failures

* and also with the case where there is exactly 1 failure
  which required a drop = FALSE to be added to matrix [] operation
Fix transformation of hxsurf objects

* and other non-neuron, non-dotprops objects
* + test