Update stwfsa to 0.2.*

[mo-fu]

A PR for an updated version of stwfsa. The Improvements are:

• No more duplicate concepts in suggestions Fixes STWFSA backend returns duplicate results #478
• Better support for long texts by using frequency and positional distribution features of concepts.
• Text Vectorizer is disabled by default to reduce memory requirements for large corpora.
• Improved Escaping of symbols in automaton construction

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

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[osma]

Thanks @mo-fu ! I tested this briefly and it seems to work as advertised.

Am I right that old models (trained with stwfsapy 0.1.x) need to be retrained? At least I got a KeyError: 'use_txt_vec' error when I tried to use an old model. No big issue, but should be mentioned in the Annif release notes.

[mo-fu]

Yes, that is correct. I have plans to add the version to the serialized files in order to have a better error message.

[osma]

Thanks for clarifying @mo-fu ! I will merge this now so it gets into the soon-to-be-released Annif 0.52.