PlayerCanJoinTeam called as a hook

[bailmast]

1. PlayerCanJoinTeam probably should be called as a hook instead of being a gamemode function
2. Fix errors when client provides a nil argument in changeteam command
3. Get rid of funny duplicating code logic comments

P.s. do not forget to remove a warning if PR merged

[bailmast]

And probably functions like OnPlayerChangedTeam should have tag "internal" on wiki

[robotboy655]

Do you have a use case for it to be called as a hook though?

I am struggling to think of a scenario where an addon should have control over what team(s) can be joined, and that's provided the gamemode would use the base gamemode hook and not their own system.

Any sort of team player limits or things like that would surely need to enforced by the gamemode?

Do you actually need this to be added, or is this a "just because" idea?

[bailmast]

So, I'm currently working on something, and I think it's important for new gamemodes to have that standard to stick with. For example, if someone is creating a new admin system, they will think, 'Ah, it's not an internal hook, so I can use it for punishments,' or they might create mini games unrelated to the gamemode's purpose.