Add Server Gun Validation

[ekulxam]

Closes #90

• Adds an additional raycast in the server receiver to prevent bad clients from shooting arbitrary targets. This raycast is 1 block longer than on client to help account for possible desync
• Removes all client references in the gun items
  • Now uses a UseItemCallback and ItemTooltipCallback for the gun items (I checked that the networking still works and the tooltip order remains)

Likely will break #68 so preferably that should be merged before this one.

[A-Random-Kitty]

An issue I see is it doesn't account for side to side desync just desync with the range which would make aiming difficult for players with high ping.

[ekulxam]

In that case, perhaps I can simply raycast to the target and check if there are blocks in the way.