Added additional pin to display name of child node being deleted

Also requires change to system.xml phrase 'Plugin/Screen/Subject/Edit:confirm_form'.
Accommodate child pin in subject removal phrase
Fixes #121
see https://github.com/QUTlib/citation-import/commit/d0dd0e5a7956cf0d3bad6286ea6c32d0309033f7
Merge pull request #104 from jesusbagpuss/patch-1

Display child-to-be-deleted when editing subjects
Fixes #123 using tjmb's diff
Fixes #101