Improve comments for unit-specific blueprint fields

[lL1l1]

Description of the proposed changes

• Improve descriptions for blueprint fields that say "used by" by adding the unit ID or class name
• Annotate SinkLower ("used by" megalith and monkeylord)
• Remove Omen's non-functional weapon opening animations

Testing done on the proposed changes

• Placed a monkeylord on a mountain peak to see what SinkLower does.
• Imported Omen's weapon animations into blender and noticed that they don't work because there are bones missing from the mesh.

Checklist

• Changes are annotated, including comments where useful
• Changes are documented in the changelog for the next game version