Christmas update:

* New, unique shove animation
* No more animated shell ejection, now uses particle-based shell ejection
* New feature: Pseudo-random recoil
* Slightly reduced idle animation intensity

Updated the position of the gun for consistency with the other overhauls.

Adjusted the placement of the weapon attachments in third person. I adjusted the weapon's scale & position a bit but forgot to reciprocate the changes to the attachments.