Fixes for when one circuit element dropped directly on top of another

[samreid]

When one circuit element dropped directly on top of another, connect one vertex and move the other vertex. Should be done for wires too.

[arouinfar]

👍

Additionally, components should not snap on top of one another.

[samreid]

The solution I was envisioning is actually more complex than I anticipated, because we may need to search out a group of components from a pivot vertex and rotate the entire group around the point.

[samreid]

Though rotating a subgroup about a vertex could come in handy elsewhere, such as rotating a group about a black box vertex. Though perhaps it would be prudent to start with a less complex solution for the simplest case (no group of connected components).

[samreid]

Initial work in 016f377

[samreid]

After the commits above, the functionality seems to be in a good position. Next I'll do broader testing then publish a version for @arouinfar to take a closer look at.

[samreid]

I fixed one new bug, and am seeing other problems related to the black box vertices--we'll have to tell them (a) it is always OK to attach to them despite other rules against it and (b) never to move them even if the postprocess step wants to.

[samreid]

More fixes above, no new issues found during testing. I'll close this one and create a new issue for broader developer testing before sharing to @arouinfar.