ViSR: Make plots size correctly

[Abigail-Yates]

This is the only solution I have found so far that achieves all 3 of these objectives:

• Plots fill their parent box
• SliceView plot resizes correctly when the controls drawer is opened and closed
• Plots resize correctly when the window size is changed

The pay off for all 3 of these working is that when the window is resized, the whole React-Grid remounts, so we see a white screen whilst the window resizes and the grid/plots re-render.

This also has added 2 'Box' components around the Heatmap plot in SliceViewer.tsx which might be less ideal for making it a reusable component.

Other solutions I have found have only achieved max 2/3 of the list.

[Abigail-Yates]

I have got a slight variation on this locally where, for the Tomography view, only the slice view remounts, which could be slightly better.

[Abigail-Yates]

Another alternative is to make the plot remount when the controls drawer is opened/collapsed instead of when the window is resized - I think this is maybe the way to go.
SliceViewer can still be used generally - a 'resizeKey' is optional so does not need to be specified. If it is specified, then the plot will remount when the value changes.

[Abigail-Yates]

Covered in #176 which also fixes issues