Improve teams management/editor in exercises (atomic testing/simulations/scenarios)

[jborozco]

Use case

Today, we can create a new Team on the fly directly in a scenario/simulation, but we can't add players in it (so the Team remains empty, useless). So the user needs to go to the team page to finish his setup.

We need a smoother approach to this and we need to think more globally of a solid pattern for assets and teams management in exercise.