Improve function CST_SplitDim for s2dv_cube

Hi,

The function CST_SplitDim needs to be improved regarding 's2dv_cube' metadata operations and avoid hard-coded dimension names.

• Avoid hard-coded dimension names
  We can see that in line 72 the forecast time dimension is hard-coded. Also start date dimension here.

• Correct 's2dv_cube' part
  Elements of 's2dv_cube in function CST_SplitDim are not correcly assigned. There are missing: $coords assignation, $Dates and $dims.

  • Add $dims result
  • Add $Dates split
  • Add $coords for new dimension

Eva