German and english are used in log messages

[ponceta]

Describe the bug
German and english are used in log messages :

WARNING Could not export to the interlis schema : Invalid dataowner reference for object 'ch000000RP000012' of type 'haltungspunkt'

This is due to the fact that we only support german INTERLIS export.

Translation of the error messages would much ease the users interactions, first iteration would be to have every error message in english.

To Reproduce
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Expected behavior
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Desktop (please complete the following information):

• TWW version
• QGIS Version
• OS

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[sjib]

I would suggest to use German / English classnames as we have German class names in the intermediary schema pg2ili_abwasser etc. and English names in the tww_od schema