Highlight relationships linked to current asset

[scp93ch]

Two parts to this, both useful but (1) most useful:

1. When an asset is selected it is outlined in green. The relationships joined to the asset should also be highlighted and the relationship's and labels as well. The relationship labels should be drawn on top of other relationships so as not to be hidden under other labels. Possibly the relationships and their labels should be drawn over the top of other assets as well.

2. When hovering on an asset it is highlighted in red. It's relationships could also be highlighted along with their labels. Again, relationship labels should be brought in front of other relationship labels.

When I have a moderately complex model I often have to grab an asset and move it around a little to see which of the spiders web of links and relationship labels actually belong to it. At least highlighting the links and even better bringing them to the front as described would be really helpful.

(this was issue #885 in the internal tracker)

Another thought is to use something like the "neighbourhood view" as shown here: https://jsplumbtoolkit.com/demonstrations/neighbourhood-views
Then you could see what an asset is linked to even if the other assets are off-screen.