[MergeDups] Don't lose other language info when merging senses

[imnasnainaec]

When senses are combined in the Merge Duplicates tool, semantic domains and definitions from all senses are preserved, but only glosses from the first sense are kept.

When two senses are supposed to be the same sense but just have the gloss in different language, combining them should keep the gloss in both languages.

Acceptance test:

• Open a project with no duplicates that appear in Data Cleanup > Merge Duplicates
• Create two words with identical vernacular form and glosses in two different languages
  • E.g., vernacular form: "vern"; first word with English gloss "worm" and second word with Spanish gloss "gusano"
  • To create these two words:
    • Go to Data Entry, select a domain, and enter the first word
    • Go to project settings > Languages > Analysis and change the top analysis language
    • Return to Data Entry, select a domain, and enter the second word
• Data Cleanup > Merge Duplicates
• Drag and drop the sense from one of the words onto the sense in the other word.
• Click the "Save & Continue" button
• Data Cleanup > Review Entries
• Verify that there is just one entry with vernacular form "vern" and that it has a single sense with both glosses