Omi

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* Fix bug that is raised if the input oemetadata does not contain the key _comment (PR74)

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* Add conversion to translate oemetadata from v1.4 to v1.5
* Add conversion option to OMIs CLI application
* Add conversion additional script that converts oemetadata from v1.4 to v1.5 without using OMI. thanks to chrwm

* Fix oeo related isAbout and valueReference field names (PR65)
* Introduce github actions: Add automation worfklows for pypi publish for test and official (PR67)
* Introduce new directory and provide some use cases and example implementation for omi usage and improve general code quality (PR61)
* Reintroduce automated testing (CI) that icludes omi unit test (parser, compiler) and more (PR69)

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* Add oem_structure module: Introcude support for multipe OEMetadata structure representations
* add new Dialect for OEM v15
* Full support (except for validation) for OEP-Metadata v1.5

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* Fix compilation of null values
* Fix parsing of lists

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* Fixed compiler for None in date fields

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* Improved documentation
* Full support of OEP-Metadata 1.4
* Support for optional fields in metadata strings