[feature] : Add grain / branch / molecule numbers to plots

[MaxGamill-Sheffield]

Is your feature request related to a problem?

With large numbers of grains in some of the images, sometimes it can be hard to tell which grain relates to which number in the associated output files.

Describe the solution you would like.

For each of the plotting stages which create unique output files with labels (i.e. grain / branch / mol number), for the key plotting image, add an option to add the object number to the images so easily identify them.

Describe the alternatives you have considered.

Colour scale images have been too difficult to read.

Additional context

No response