Add newlines to error messages caused by exceptions
Fix UB, which caused garbage value in the xml path in mdb on BSD
Reintroduce <root> vertex rewriting

Reintorduce c348f1b

It was removed accidentally by 921ff4
Print the original metafunction call in bt
Pass metaprogram root name in its constructor
Rename a variable to better reflect its type
Print the evaluation result only when the simulation ends
Create mdb command handler only once
Make things more clear when running evaluate
Merge remote-tracking branch 'r0mai/master'