FMI3 support

[clegaard]

TODO

• Setup testing of the CLI and generated FMUs in different backends.
• Complete the FMI 3.0 support for unifmu, including the synchronous clocks interface
• Extend some of the backends with this support (we will likely not be able to finish this and hope that some of you will help here).
• Prepare some examples of unifmus using synchronous clocks. Likely in the python backend. Add them to https://github.com/INTO-CPS-Association/unifmu_examples
• Generalize the endpoint stuff in unifmu to enable the FMU to connect to the backend running in a different computer, to enable distributed co-simulation as long as one computer gets all the fmus and has connectivity to the backends in the other computers.
• Update the documentation to match the above.
• Ask a few peers for reviewing the documentation and code.
• Make new release.

[clagms]

@thmq are you still able to contribute here?