WIP...

The assets system is used to load:

• project files (.gemprj)
• sprites (.jpg, .png, etc.)
• preferences files (.toml)

Preferences Loader

• We added a new asset loader that can read any .TOML file in the preferences folder.
• Currently the only preferences file that is supported is _comment_types.toml, but other preferences can be easily added.
• Preferences are saved in the art assets folder under each site's preferences folder, e.g. in /gsgo/gs_assets/art-assets/preferences/_comment_types.toml.
• The preferences system can readily add other .TOML and .YAML file assets. (.YAML support is available but not implemented yet)

See #763