Disable triggering Objectives during setup time

[zonical]

Request from HiGPS.
To allow for maximum flexibility (Creators.TF allowed triggering progress during setup time), this can be an optional feature implemented with a ConVar (zctf2_allow_setup_trigger). This could be expanded to not trigger Objectives during round end and waiting for players (zctf2_allow_roundend_trigger, zctf2_allow_waitingforplayers_trigger)

If CSGO support is added later on, the same could be done for freeze time and round end.