NEW Diet Lock option + Balance

New features:

• Added a new simulation option: DIET LOCK (When ON it prevents the Diet Gene from mutating).

Balance:

• Buffed small creatures because carnivores  also eat.
  
• Creatures can no longer reproduce or grow using fat.
  
• Plants now reduce fat instead of giving a very small amount.
  
• More balance changes.
  

Misc

• Some small optimization.
  
• Some bug fixes.