SCT Sheets: Session persistence of Time Column Widths per Sheet [1]
Bug Number: n/a
Release notes (y/n): maybe
For Release Nums: 7.2, maybe 7.1.x

This commit represents a second iteration of requirements for this TVA SCT 
task:

  (TVA 39) Improve the width of the SCT columns when using multiple sheets.

Time column widths applied to horizontal-time SCT views are now preserved 
ON A PER SHEET BASIS within the RiverWare session.  These widths, however, 
are not preserved in the SCT configuration file.

This column width session persistence makes use of these two new maps in 
the SctConfig class:

  // Sheet-Specific Applied Time Column Widths
  mutable QMap<QString,IntSeries*> _noAggTimeDataSheetColWidthSeriesMap;
  mutable QMap<QString,IntSeries*> _aggTimeDataSheetColWidthSeriesMap;

... these QMaps are indexed by the Sheet Label text.  Associated with each 
sheet is a dynamically allocated IntSeries -- that is, a Series<int> instance.
 There is one of these maps for each of the two horizontal time SctViews:
Aggregated and Non-Aggregated.

The timestep size and time range of these series is set by this method:
  void SctModelData::resyncSctConfigTimeColWidthSeries (bool agg);

Access to these IntSeries is done via these methods:
  void SctTableModel_THorzStd::recordColWidth (int col, int newWidth);
  void SctTableModel_THorzAgg::recordColWidth (int col, int newWidth);
  int SctTableModel_THorzStd::recordedColWidth (int col) const;
  int SctTableModel_THorzAgg::recordedColWidth (int col) const;

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