Enable gather mods to fix teams in case of captains not picking proper teams

[swalk1001]

This is a feature in the old gather system that has been lost in translation to the new one. Thankfully it's not too often that this feature is needed, but it is definitely necessary sometimes. After returning to the game I've experienced the need for it a couple times.

Feature description:

• When captains are done picking the teams, gather moderators should be able to switch players between the teams somehow.