Omi

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* Fully rewrite OMI and implement the json schema spec only, remove python class based parsing (104)[https://github.com/OpenEnergyPlatform/omi/pull/104]
* Add a new conversion functionality to convert form v160 to v200 oemetadata [(111)](https://github.com/rl-institut/super-repo/pull/111)

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* Reorder metadata fields after the json input was compiled & prevent removing context fields if they are Null (96)[https://github.com/OpenEnergyPlatform/omi/pull/96]

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* Introduce OMIT_NONE_FIELDS in JSONCompiler class to ease removing / keeping none values in the metadata. By default None values are kept. (72)[https://github.com/OpenEnergyPlatform/omi/pull/72]

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* Fix datetime parser (PR87)

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* update parser for v15 to handle former v13 key names, also update outdated License (data-)class in oem_v15 structure. (PR77)
* change the validation to return a report and enable report file creation option to the arguments of validation method. (PR81)

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* Add validation and helper functionality - validation based on json schema and the oemetadata schema files that are published for each release (PR63)