UI: Improve connector placement on map

[updraft0]

As a first pass, it seemed easier to draw connections between systems based on only the following pieces of information:

• the position of the "from" system
• the position of the "to" system
• the "rank" of the connection on both sides (so e.g. whether it's the first of a single connection or the second of five)

This only works nicely up until you need to move the connections around from one side to another - where this breaks down because connections remain at the same "rank" no matter which side and are therefore incorrectly positioned. The position of the systems relative to each other is also important because connections shouldn't get crossed over if A is connected to both B and C, but C is above B on the map (y-coord) wise. The static ranking computed in the database is not useful in these cases and a more dynamic algorithm based on the map coordinates of systems needs to be developed.