Modpack Update Checker

Internal Changes:

• Moved remaining config login in MpucClient to MpucConfig and ConfigInstances

There were major internal changes with this version, and any bugs will be quickly resolved.

• A JSON based config has been added, replacing the old modpack-update-checker.txt file. Old configs still work, and will NOT be migrated as of 0.6.0.
• EarlyLoader disabled, security risk.
• The JAR is now signed!