Pycatsearch

In the Catalog Info, the context menu allows locating the catalog file on disk and downloading missing or changed entries.

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The release contains a fix for the regression previously fixed in [v5.1.7](https://github.com/StSav012/pycatsearch/tree/v5.1.7).

Fixed a crash when selecting/deselecting a substance in the list in the main interface.

Added support for localization of labels. Preparing the translations.

- The search is now instant. There is no need to click the _Show_ button.
- The substance choice can be more precise via double-clicking a line in the list of the substances. If there is more than one substance behind the line, an additional dialog appears.
- When the filter of the substances' list is empty, the checked items are at the top.
- There is no search timeout anymore, for the search is fairly quick anyway.

Fixed:
- a crash when saving a downloaded catalog,
- the Substance Info dialog shown only once for a substance in the list,
- the Preferences dialog geometry not saved,
- search by ID didn't work.

Added:
- a link to the CDMS web portal in the Substance Info dialog (see the ID),
- customizable URL templates to browse substances by InChI key from the Substance Info dialog,
- search by InChI key.

Changed command-line options related to the search by InChI key.

It's getting harder to ensure compatibility with old Python versions day by day. This time, the app crashed without a traceback on copying.