Accommodate duplicate IDs

[super-structure]

Currently, if there are duplicate @ux-context-string values in the map, the entire JSON file is not created (or, rather, is just empty).

This can happen even if the same topic is just included in a map twice.

[super-structure]

Categorizing this as a bug, as this even occurs when a topic is included in a <reltable>, which is almost always going to cause the mapping to fail to be created.

[super-structure]

The previous PR corrected the reltable issue but did not address the potential for duplicate entries of the same topic or same @ux-context-string value causing the JSON file to not be created.

• if the same topic is included more than once, just ignore other entries
• if the same@ux-context-string value is used more than once, only use first entry and give warning to the user that the others are skipped