Aerofiles

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* igc/reader: fix for HFTZN to handle timezone that is not integer
* igc/reader: add "datetime" and "datetime_local" to fix_records to
deal with UTC and local time correctly. Please read "How
to read an IGC file" for a detailed explanation.
* igc/reader: added flag "skip_duplicates" to remove B records with
identical time.
* improved documentation for IGC

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* messed up v1.3.0 deployment. Redeploy as v1.3.1 without any changes.

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* openair/writer: first implementation of type "airspace". Others are missing
* openair: implement extended openair format
* openair: various smaller bug fixes

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* seeyou/writer: fix in writer to use ";" as delimiter for pics

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* seeyou: handle newer file formats including rwwidth, userdata and pics.

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* v1.1.0 failed to be published because of wrong GitHub action. Fixed