Ask a user to compress the output only if an outputfile is specified

[Chrisp485]

Feature request

Description

As a user I only want to be asked to compress my outputfile, if an outputfile actually gets generated. When #2800 is completed, the importers write the output to stdout if no outputfile name is given.

Acceptance criteria

• [ ] Implement for all activley used parsers
• [ ] Adjust parserdialog
• [ ] Adjust parserdialog tests

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