Feature: GP Shop PR Cleanup

[RyanYappert]

Cleans up and preps the existing GP shop code from @Sehkah and @pacampbell for merging.

• Ensures constructors and serializers properly instantiate their members and strings.
• Removes raw references to localhost and constructs the necessary paths from the game settings.
• Removes possibly copyrighted material from the repository. This should be archived separately for legal reasons.

Since some of these handlers are still in a very early state and expose hardcoded functionality, they've been blocked off from players with a ResponseErrorException.

Checklist:

• The project compiles
• The PR targets develop branch