[SCIP] make branching constraints show up in the visualization(visual/vbcfilename) of the branching tree

[myroslav]

Dear SCIP community,


I have a branch and price algorithm and I am adding some constraints 
when doing branching at a node in particular I have a "marker" 
constraint handler that stores  a single constraint for each branching 
decision whose data has information about the branching decision. I 
visualize the branching tree using visual/vbcfilename parameter which 
makes scip making a vbc file which I then convert to .dot using vbc2dot 
tool and visualize the branching tree using graphviz. I wondered how I 
could make my marker constraints show up in the visualization. Since I 
have just one marker constraint per one branch, this should be possible, 
just like in the default variable scip branching.

Thanks,
Myroslav