CustomItems support and fixes

[Michal78900]

Changelog:

• Removed Serpents Hand methods, because it no longer can spawn instead of NTF
• Added support for giving / spawning CustomItems
• Probably fixed OutOfRange exception (from my testing it worked without the issues)
• Added Methods.cs class for UIU methods and custom items giving
• Renamed many properties from UIU to Uiu
• Some code tweaks like replacing Ammo config to Dictionary