Support "portal" visualization for connections

[jonnor]

"Portal" meaning that the wire for connection exits an output port, goes into a terminal (which can be named, like "api-token"), then on the other side comes out of a terminal and then into the inport

[SomeComp]----o api-token

...other stuff in the middle....

api-token o---[AnotherComp]

This paradigm is standard in electronics design automation for instance.

A major usecase for this is configuration options which need to go to many components in many different places of a graph.

[jonnor]

The connection/edge naming feature should probably be separate from this. Because it is also useful to show in debug logs/flowtrace, and when doing grey-box testing.

[bergie]

Related #288 and #371

[jonnor]

Selecting such a connection should highlight not just the terminals on both ends, but also provide a (potentially a bit weaker) visualization of the whole connection - to easily see what is connected where.

[ensonic]

If we can mark outputs as 'portals' then when editing a component, there could be a dropdown icon to select from the portal list. This would create the connection internally.