Changes associated with new interpolation routine:
 - replaced the old qcts.InterpolateOverMissing with a new
   version that uses qcutils.contiguous_regions to find
   blocks of missing data less than maxlen long and to
   fill those gaps by linear interpolation
 - implemented option to write netCDF files with 1 or 3
   dimensions, 3 is the default, the number of dimensions
   is read from the Options section of the control file