Fix bug in copying QwtWorkspaceSpectrumData

It now sets the distribution flag correctly.
Refs #10639
Require the distribution flag rather than it being optional

Refs #10639
Use an enumeration for distribution settings.

Currently reproduces what it did before.
Refs #10639
Remove dead menu actions that were never attached to anything.

Refs #10639
Add a configuration option for global distribution plotting

Refs #10639
Use global configuration option for distribution plotting.

Refs #10639
Add normalization options to graph context menu.

Refs #10639
Add context menu options to set the distribution status.

Refs #10639
Only use distribution flag for histogram data.

Refs #10639
Don't show Normalization context menu option if not applicable

Refs #10639
Reword option in ConfigDialog

Refs #10639
Merge branch 'feature/10639_plot_distribution_option' into develop