Make invisible spawns hidden. Closes gh-627
Remove "Can't re-enter spawn" task.

This test task is incompatible with additions to War regarding teams.

This method of preventing players of receiving spawn protection is
currently extremely buggy and there has to be a better way to fix the issue
at hand.

@taoneill please email me if there is any serious reason this task is
needed, otherwise it just deteoriates from the War experience. Numerous
times I have played War, I have been bumped out of a warzone even due to
this. There seems to be no need for it. I can revert this commit if needed.

One possible solution could be disabling all protections for anyone who
returns to their spawn, such as like how loadout switching is prevented
after leaving spawn. Another solution could be preventing multiple teams
from taking a flag while another flag is on the run.

Please leave your ideas in the comments or email me.
Add support for multiple spawn points. Closes gh-628.

/setteam <color> now will add an additional spawn point if the team already
exists.

When a player joins a team in a warzone, they will be sent to any one of
their teams spawn points, picked at random.

This change required major modifications to the underlying teams subsystem
in order to support multiple spawn points for the team.