Connect transitions to existing transitions

[franzlst]

To save time during creating connections between outcomes and states it should be possible to connect a transition to existing transitions.
Thus if two outcomes of a state (or different states) have the same target state they can share the same "line" in the visualization.

The issue is a duplication and splitting of mantis issue https://rmintra01.robotic.dlr.de/mantis/view.php?id=2222.

An example for further understanding
State-A has a transition to State-B and State-C also should have a transition to State-B. Now, it would be possible and useful to draw an transition from a outcome of State-C to State-B by drawing transition until it intersect with the transition between State-A and State-B. While drawing the transition and hovering of the existing transition a mark could indicate the possibility to junction both transitions at this point.

Originally created by @Rbelder at 2016-03-02 13:42:23+00:00 (moved from RMC internal repository)