feat: support of inverse properties in parser function and Designer

[gesinn-it-gea]

This PR introduces support of inverse properties (-Links To) for both, the parser function and the Designer.
Also contains the fix for the Designer option export graph.

The corresponding API functions have been expanded for this purpose, but are to be replaced in future - in a separate PR - by APIs provided directly by SMW (SemanticMediaWiki/SemanticMediaWiki#6145).

[gesinn-it-gea]

fixes #15 and #1

[krabina]

thank you for the PR!

[thomas-topway-it]

a notable work, thanks a lot ! Could you please clarify the use of the second multiselect in the Add by properties Dialog, as below ? (specifically in conjunction with the first)

[gesinn-it-ilm]

@thomas-topway-it We enhanced the By properties dialog to provide more control over the graph generation process — users can now explicitly choose which nodes (pages) to include in the graph for the selected properties.

The By article option works similarly, but there the user selects only the pages (nodes), and we automatically fetch all direct and inverse properties for those nodes to build the graph.

In contrast, the enhanced By properties dialog allows the user not only to select which properties to visualize but also to define the set of starting nodes - giving more flexibility and precision.

Perhaps it would make sense to consider merging these two approaches into a unified dialog for a cleaner UX? What do you think?