Merge branch 'terencehill/gameover_stuff' into 'master'

Merge branch 'terencehill/gameover_stuff' into 'master'

gameover stuff

* Assault: when the first round ends show the message "Objective destroyed in X minutes" and block the game for 5 seconds before starting the other round in order to show objective destruction
* When a round ends block players and switch to 3rd person view (affected game types: Clan Arena, Domination, Freeze Tag, Invasion, Onslaught)

Implementation details:
* intermission_running and gameover are now 2 different conditions
* if set gameover has the effect of blocking players and triggering 3rd person view (eventchase); server must reset (respawn) players and vehicles (round_handler takes care of it) when resetting gameover to false.

See merge request !368