Fixes#15468
Also improves the error messages if the string isn't hex, because saying that the color value is negative is just a side effect of the implementation and tells you nothing.
Should fix issues some of us have with `misc/dist/uwp_template/AppxManifest.xml`
always showing up as modified.
Might cause issues on Windows due to the removal of BOMs or change of line endings
in some of the Mono, UWP or gradlew.bat files, we will test and adapt if need be.
- Allow non-public fields to be exported as well (to avoid confusion).
- Set PROPERTY_HINT_RESOURCE_TYPE for resource derived fields.
- Support enums and automatically fill PROPERTY_HINT_ENUM's hint_string for enum fields.
