title: Delphi TClientDataSet sorting (insert) issue
body: <p>as far is I know sorting in a ClientDataSet works over the indexDefs.
  I can add an indexDef, set the field(s) I want to sort, and over the ixDescending property I can define the direction to sort.</p>
  
  <p>I have a ClientDataSet connected to a dataSource which is the source for a DBGrid.
  When I now insert a new record in the ClientDataSet, it's either inserted at the top of the table (ixDescending = false) or at the bottom of the table (ixDescending = true).</p>
  
  <p>But I want a descending order AND new records should be at the top at the table - not at the bottom.
  I tried to change the the indexDefs at runtime to achieve this - but without success.
  Somebody has an idea how to do this?</p>