Weight System Rework [READY FOR MERGING!]

* __Updates weight system to run on grams instead of 1/4 lbs internally__
* Updated weights of _everything_ to be more realistic
* Weight for ammo is now measured on a per ammo basis
* Lowered the amount the player could carry to a realistic amount (don't worry, the weight of everything has basically dropped by a factor of 4, so in most cases you will now be able to carry _more_)
* New carry weight is much more dependent on STR
* Cleaned up a lot of duplicate code
* Overburdened players take pain over time
* Added a new option to allow players to toggle in-game display from lbs to kg
* In-game weights are now displayed to the 1/10th of a lbs/kg
* Inventory weight now tracks ammo/food inside of weapons/containers
* Vehicles weigh less, meaning collisions are slightly more damaging
* Fixed issue #2326 
* Added missing chitin armguards recipe