Based (and solves) Mantis ticket:
http://www.freecadweb.org/tracker/view.php?id=1643
The ticket refers only to redundant, and ask for deletion.
Two commands are created, one for redundant constraints and other for conflicting constraints.
As usually removing one constraint of the "at least one" is sufficient, the implementation selects the constraints (but does not delete them).
The user therefore easily identify the constraints involved and decide to delete them.
This implementation takes into account the edit->Actsketch that ViewProvidedSketch creates for solving, as it is this instance the one that generates the messages in the Sketcher Taskbar.
No buttons in the toolbar by default (can be added by the user), but an hyperlink in the solver messages which triggers the selection of the appropriate command (conflicting or redundant).
