Features:

- Changed the solver pre-processor to include it's state in the crash report when it encounters a contradiction.
    - This makes it easy for a loader developer to reproduce the solver state in order to debug it.
- Bumped provided version of Fabric Loader from 0.14.24 to 0.15.3
- Added MixinExtras as a jar-in-jar mod inside of quilt loader.
    - This is an additional library for creating mixins in more expressive and compatible ways.
      For example "@WrapOperation" is a more compatible way of doing "@Redirect", if you don't need
      to replace the method call in all circumstances.
      For more information please see the MixinExtras wiki page: https://github.com/LlamaLad7/MixinExtras/wiki
    - You can use the system property "-Dloader.disable_builtin_mixin_extras=true" to disable loader's builtin
      version of mixin extras. As such mods that use mixin extras are encouraged to add it as a dependency in their
      quilt.mod.json to make the crash more obvious when a user has disabled it but a mod requires it.
- Re-added a previous fix that was added in 0.18.1-beta.1 and accidently removed in  0.18.1-beta.58:
    - Changed the entrypoint hook to use the old fabric class when running in versions before 1.17.
        - This allows NotEnoughCrashes to redirect our entrypoint
- Added a new system property "loader.overrides.generate_file"
    - You can enable this by adding " -Dloader.overrides.generate_file=true " to your Java arguments.
    - This will create a new empty override file in the right place if one doesn't already exist.
- Added a new system property "loader.debug.override_file".
    - You can enable this by adding "-Dloader.debug.override_file=true" to your Java arguments.
    - This logs a few messages when loading an override file, to help when debugging.

Bug Fixes:

- Fixed a solver pre-processor bug where chooseBasedOnOnly didn't check for new constants, resulting in later contradictions.
- Fixed QuiltClassPath.getResources not always returning all paths, when multiple mods ship the same file.
- Fixed the forked gui not launching correctly on java 8 due to argument files being unsupported.
