feat(editors/SingleLineDiagram) Allow movement of bays

[danyill]

Allow movement of bays, see #456

I will be very happy to take a review and make corrections. I will be happy to be educated. Perhaps I could convince @dlabordus to take a look (hi! 😉).

Note that I have used SVGGraphicsElement instead of SVGElement because many methods associated with graphical objects are not available in the TS types for SVGElement (see MDN). I have resisted the urge to replace this more widely than required to satisfy the compiler.

It seemed for the time being that the best way to access bay properties was on the bay text rather than the rectangle drawn for the bay as this overlaps other objects. This is not consistent with what is done elsewhere where we click on the graphic. Happy to take some ideas about a better approach.

The ssd file included on the issue might be helpful for tests.

moving_bays.mp4

I'm not sure how to write a test but I'm happy to have a go.

Note: This works on "some bays" for me but not all of them, the getBBox appears not to always be correct -- I haven't yet looked into this.

[danyill]

There is also an "annoying flicker" during re-render after a change in coordinates that I need to look into.

[danyill]

Looks to be obsolete, see later #504