LMS updates

It addresses some of the points of #2419

1. periodically show waypoints for leaders for a few seconds (by default they spawn every 30 seconds, randomized 25 / 35 so that it's less predictable)
2. increase player respawn delay based on the number of lives less than the leader (only with 3 or more players)
3. attackers receive a fraction of health removed from enemies based on the number of lives less than the enemy
4. HUD panel showing number of leaders and an icon when leaders are visible and lives difference