Added "snpc_combine_guard_laser_accurate" and "snpc_combine_guard_fall_over" cvars

- Improvements

Updated to new leaked model, this means:
- Flinch animations, including a falling sequence, and a death animation
- A new melee animation
- Armor will now visibly break
- Model might look a bit weird
- The animations can sometimes fail and do weird things

AI Improvements:
- Lone combine guards will now always chase the enemy
- Combine guards can now fire smg grenades from their wrists
- Simplified melee attack system, they will now melee enemies more consistently