Correct labels in yaml model parser

Summary

This is a correction for #77 (moved).

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There is a unit test.

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CHANGELOG.md

@@ -130,6 +130,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * `TableImporter.check_missing` in case of array-valued fields in table
 * YAML model parser has better description handling.
+* YAML model parser shows "LinkAhead" and "the yaml file" in its comparison display
+  instead of "old" and "new".
 
 ### Documentation ###