Add and remove individual hands

[stilnat]

Summary

Following the inventory rework, this makes hands works properly when they are added or removed.
Currently, hands are controlled by a unique script, Hands.cs. This add another script, Hand.cs, representing a single hand.
Hands.cs becomes a controller for each hand on the player.

Server and client methods are also properly separated and varaibles synced, allowing only server to do things such as removing hands.

When a hand is removed, if it was the active hand, then another available hand become active, or none if there's none left.
It integrates nicely with interactions, as with no hands left it won't throw exceptions if the player tries to interact.

This is necessary to move on with basic health, as this will allow loosing hands properly.

File changes

• LeftHand.prefab and rightHand.prefab now don't have the item component nor rigidbody.
• Adding two prefabs for left and right hands, basically a copy of the old ones.
• Added an assetdatabase for bodyparts (which generate 15+ extra files)

https://youtu.be/6u2Og_aA63w

TODO

• Add adding hands properly
• Add server command to test adding hands properly.

Known issues

no known issues

Fixes (optional)

no known fixes