"comment2">mGridCoordinates/getVerticalAxis - get vertical coordinate data

 if 3D, get vertical coordinates for the specified timeIndex
 if no vertical transform is present, then get 1D coordinate axes.
 Specify 'verticalLevel' to retrieve data for specific level.

 Method Usage:  
   vertAxis=getVerticalAxis(mGridCoordinatesObj)
   vertAxis=getVerticalAxis(mGridCoordinatesObj, timeIndex)
   vertAxis=getVerticalAxis(mGridCoordinatesObj, timeIndex, vertLevel)
 where,  
   mGridCoordinatesObj: mGr