Added config option: ReusePlotInstances (On/Off), re #8091
Support option 'ReusePlotInstances' in MantidPlot UI, re #8091
Added individual close slice viewer win, re #8091
tooltip, and try to keep positions, re #8091
Nicer error handling/messaging - spectrum and slice viewers, re #8091
Nicer error handling/messaging - color fill plot, re #8091
comment out, not really possible, cause of plot differences, re #8091
fixed initialization, re #8091
fixed window name issues on windoze, re #8091
Fix crash when users close plot windows, re #8091
Merge remote-tracking branch 'origin/feature/8091_control_spawning_of_plot_windows'