Spectator Slot Briefing

[SamLex]

Spectator slots currently get a default briefing (or the Zeus briefing, not sure which). It would be good if they got the briefing of the active player side or, failing that, no briefing at all.

[shadow-fa]

This would require the concept of an active faction.
Because of the number of possible factions/briefings and the fact that multiple factions can be active at the same time, this would add too much complexity and I think no briefing should be shown instead.

[NikkoJT]

PR #161 seems to be working correctly. In the dev version, spectators see no briefing, with no error message. Zeus still sees a briefing. The F3 Admin briefing tab is still available for spectators.

[SamLex]

Great, thanks @NikkoJT. I'll close this issue when FA3.5.2 is released.