Freezetag updates

All the changes:

• apply spawnshield for 1 second after you've been revived (spawnshield is lost after you fire)
• reduce auto-revival time based on manual revival progress; it fixes progress bar apparently stuck for some time after a failed attempt to revive. To compensate for the increased ease of revival, don't award an extra point for revival (just for the time spent reviving)
• don't reset autorevive progress when a frozen player falls into the void
• limit hit force considered at once to reduce autorevive time, e.g. when you have the Strength powerup but also with weapons that fire multiple projectiles at once (crylink)
• reduce g_freezetag_revive_auto_reducible_forcefactor to make revival of frozen enemies by hitting them even more difficult
• increase pre-round time
• use an alternative lower revive speed if g_freezetag_revive_time_to_score is active but make so that revivals can be resumed at the same speed from the current revival progress: previously a revival always took 2.5 seconds, now it takes from 0 to 4 seconds
  EDIT: NOTE: in master, revival can be resumed at the same speed from the current manual revival progress if resumed right after a previous attempt.
  If resumed long after the previous attempt (when the auto-revival progress is greater than the manual revival progress) the revival speed is decreased so it takes 2.5 seconds to revive (the time spent in the previous attempt is ignored).
  This change fixes this weird / inconsistent behaviour by always applying the same revive speed.