Add "Delete label instance" entry to label instance context menu
Summary:
- Add "Delete label instance" entry to label instance context menu
- Rename "View only" to "Hide everything but this"
Test Plan:
- Right-click on label without other instances (no "Delete label instance" entry)
- Right-click on label instance ("Delete label instance" appears and does so)
Reviewers: floca, O1 MITK Reviewer Group I
Reviewed By: floca, O1 MITK Reviewer Group I
Maniphest Tasks: T29556
Differential Revision: https://phabricator.mitk.org/D819