Modpack Update Checker

• Config schema version has been bumped to v2, old configs will not be migrated as of 0.7.0.
• New update checker format! Current update checkers will continue to function.

Internal Changes:

• Moved changelog and latest version logic in MpucClient to OnlineInfo
• Added a debug screen only viewable in a development enviromnent.

API:

• Added a basic API for viewing the modpack name, the current modpack version, and the latest modpack version.