Related to LDEV-2329

If an activity is set to define later due to editing the activity in Monitor, we must make sure that there's a very clear alert to the monitor that the flag is set because otherwise students would get stuck and the teacher won't be able to know unless the student inform the teacher.

In terms of what the indication might be, i was thinking to set the background of the define_later activity to red or an flashing icon over the activity so it's very clear to the teacher that action is required.

Also, when opening the activiity (and this might require a change in every tool) we need to show in the summary tab that the define_later flag is on.