Addition of a scalebar to 3D view

[alanspencer]

Is your feature request related to a problem? Please describe.
The idea is to implement a scale bar, that displays a rectangular box (= "the scalebar") scaled to the current model view with the numeric value of the scale bar shown. This would be aimed at quickly producing figures for plates straight from SPIERSview.

Describe the solution you'd like
The scale bar should have customisation:

• position on screen (top left, top right, bottom left, bottom right);
• colour of scalebar and value text;
• thickness (y-axis) of the scalebar;
• horizontal or vertical transformation.

The scalebar should be a toggle on/off option from the main menu and have a key shortcut. Configuration of the scale bar should be via a dialog with form.

Describe alternatives you've considered
None.

Additional context
None.

[alanspencer]

Putting this on hold for the moment as the upgraded Scale Grid system now copes with many of the situations that this would have been used for.