When a simulation throws an error, show causing BE

NOTE by Michael: 1 is possible and not part of this feature.

1. Possibility to copy and cut-and-paste pieces of CPN models. Currently, only single transitions can be cloned
2. Making the debug easier. When a simulation throws an error, it would make the life much easier to know the firing of which transition caused the error along with the variables’ binding used

1. Nope; check Cloning Groups of Elements
2. It is not always possible, but sometimes it could be… I’ll change the title to reflect that.

Thanks about point 1.

I was not aware of it because I was expected the usual way of copying as in other applications for Windows.

Under review

Reopened as 4 goes out soon