convergence status/loading bar

[bchasnov]

The recent version displays every iteration of the solver even before the solution completely converges. We therefore need to be more cautious about when we are displaying nominal/yellow trajectories. A few new things are needed

• gray-out the trajectory until the solution has converged, and do not allow committing non-converged trajectories.
• status bar information (percent done, loading bar, the likes)

This will be important especially with multiple trajectories. It will get crowded and we should only see the valid trajectories.