* Further async changes
- SaveServer & Backup Server are now async
- Anything that ties in with SaveServer saving (Such as callbacks) are now async
- Various async util methods added
- Removed two wrapper methods and switched code over to use the actual method
* Update test
* Added a new Fody plugin to add to every model class the JsonExtensionData attribute
* retargeted fody plugin to netstandard for msbuild runtime
* Fixed runtime issue
* Fixed property check for new extension data properties
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Co-authored-by: Alex <clodanSPT@hotmail.com>