Clinguin

- The code was reorganized to simplify the extension of the server functionalities in each backend.
- the `clinguin-state` was removed and now the domain state is created by multiple constructors
- the class `UIFB` was removed and functionality was separated
- the abstract backend was removed to avoid confusion
- ❗❗❗ `_b` and `_c` tags are replaced by `_any` and `_all`
- Added documentation for creating your own backend and using the angular frontend

First official clinguin release. Check out the [documentation page](https://clinguin.readthedocs.io/en/latest/) for detailed information on the system.

This the first Beta release of clinguin.

We hope this version allows people to try the systems and give us feedback for further development.