Modified TSelectionSearchDlg to work with interface to TSelectSnippetsFrame as changed at revision 3954.
TSelectionSearchDlg's own public interface also changed to receive a ISnippetIDList parameter instead of TSnippetList.
Modified TDialogMgr.ExecSelectionSearchDlg re changes to TSelectionSearchDlg. NOTE: some temporary changes were made here to convert an TSnippetList to ISnippetIDList.
