SCT Sheets: Column width operations and stability [TVA] [1]
Bug Number: n/a
Release notes (y/n): Yes
For Release Nums: 7.2

This commit was originally in a "SctSheetCols1" temporary GIT branch, on 
top of the "SctUndockSheet2" temporary branch.

The following two major changes were made to SCT series slot tab column 
width management with respect to SCT Sheets:

(1) For horizontal-time SCT views (aggregated and non-aggregated), where 
slots are SCT rows, switching to a different SCT Sheet was unnecessarily 
resetting the time column widths to the default width.  (See note below).

(2) The following column width adjustment operations (for which toolbar 
buttons are presented, as well as menu items), now operate on ONLY the slot 
columns in the current SCT Sheet.  (This is relevant only for horizontal 
time SCT views, where slots are SCT columns).  Note however that ALL slot 
columns can be adjusted by operating them with the final, "All Slots" 
sheet tab selected.

  (a) Resize Columns: Set All to Selected Column Width
  (b) Grow Columns: Fit Data
  (c) Resize Columns: Fit Data
  (d) Reize Columns: Fit All (header and cell data width).

The first of these operations is now disabled when switching away from the 
SCT Sheet having the selected column (in vertical time SCT views, where 
slots are SCT columns).

Note for (1):  This undesirable behavior was caused by the fix to Gnats 5877 
("SCT display issues when removing a slot", Jan 2017) which was reported with 
RW 7.0.1 (after the upgrade from Qt 4.8.5 to Qt 5.5.1).  The part of that 
fix which caused this problem was unnecessary for vertical time SCTs.  See 
the change in method: SctView::updateSerSlotTabSlotVis().