Tweak cvar defaults

This changes the default value for a few console variables :

• movebob: 1 => 0.25
• playersforexit: all => 3/4
• advancemap: next => random
• cam_speed: 0.3 => 0.4
• cam2_speed: 0.3 => 0.4
• timerres: classic => mania
• fov: 90 => 100

Additionally, gr_modelinterpolation no longer has an "always" option and now is just on/off, defaulting to "on" (formerly "sometimes").