Re #7205. Change the way column sizes are setup.

Since QTableView likes to look at all cells to calculate the width.
Changed the hint for how to calculate column sizes to be "Interactive."
Re #7205. Adding back in reasonable default values for column widths.
Re #7205. Added the missing 5 characters to fix the bug.

Thanks for catching this one.
Merge remote branch 'origin/feature/7205_sliceview_performance'