Release of SSP 2.0.1

The SSP 2.0.1 standard has been released.

This is a maintenance release with various bug fixes and clarifications of the standard. The corresponding schema files are mostly unchanged from the 2.0 release, with the exception of the type for enumeration values.

In addition to the specification and complete package, the full set of changes can be viewed on GitHub: https://github.com/modelica/ssp-standard/compare/v2.0...v2.0.1