LBP3 Challenges

[Toastbrot236]

Implements the ability to have the server read and return the contents of a ChallengeConfig.xml file from the working directory to the game if requested. If no config file is found, the server will default to a hard-coded config which contains and attributes all 14 challenges.

This closes #426.

Score submission and fetching for challenges and adventures will come in a seperate PR.