Anchor connections to center of components.

[bemosior]

trafficstars

This PR suggests an adjustment to the anchor points of component connections.

Previously, nodes connected to the top center or bottom center of components.

This PR, suggests that nodes connect to the center of components.

I believe that centered anchors are more pleasing to the eye and along the lines of what users expect to see. While there is a legitimate argument of function (when vertical spacing between two components is tight, it could conceivably be useful as a way to distinguish which component is above the other), I would offer the opinion that other solutions (redistributing components vertically to increase distance between them, or increasing the vertical size of the map) are preferable.

[cdaniel]

The connection looks much better. On the other hand, I am very afraid that this situation (which happen for me when I am rearranging components on the map), will be easy to miss. I think I will have to implement https://github.com/cdaniel/atlas2/issues/113 before merging this PR.