Respawn dev A

[NikkoJT]

This PR will hopefully:

• enable respawning with a parameterised ticket system
• prevent outright death from injury or bleedout, while allowing downed units to force their own death after x minutes of being down
• allow group leaders to deploy a side-specific respawn beacon object, which respawned units can teleport to
• allow respawned units to spectate their team while waiting for reinforcement, and enter full spectator after reinforcements are expended

TODO:

• - test it
• - add f_respawnBase and f_respawnTerminal objects to the template
• - add default side respawn markers (invisible) to the template (required for BI respawn system)
• - add briefing stuff
• - add Scripted EH calls for down/up

[NikkoJT]

Currently respawn beacon placement is a hold action, but it could also be moved to the Player Actions briefing tab.

There is currently no safe respawn handling for mapclickteleport - the action will be lost if you die while having it. Mostly we don't have teleport available more than once so this might be fine.

Actually MCT could be moved to Player Actions as well, that would make it easier to deal with

[NikkoJT]

To fix: the force respawn button display will be created repeatedly by the medical loop. This is actually desirable in case it's accidentally closed, but it needs to only happen if the display isn't already open, to prevent stacking.

edit: done