Also display deleted records when generating Solicitor reports in "diff" mode

[ohecker]

As a user of Solicitor when I am creating reports in "diff" mode (see https://github.com/devonfw/solicitor/blob/master/documentation/master-solicitor.asciidoc#72-determining-difference-to-previously-stored-model) I also want to see any records that appeared in the old report but not in the new one.

Currently only new records and changed fields are marked. There is no information on records that disappeared. As this info might be important for checking the differences it should somehow be included.