Merge 7.6.1 upgrade changes to the dev branch

[maven-release-plugin] copy for tag dspace-7.6.1

Resolved these conflicts: dspace/config/default.license - The version in upstream has default "DSpace University" text and removes linebreaks. I retained our version which has linebreaks. If our license renders improperly somewhere, we might remove linebreaks.

dspace-api/src/main/java/org/dspace/core/Email.java - Used the upstream version, which has been reorganized by Mark Wood. Our version contained his earlier fix for empty subject lines, which I believe is not necessary after the reorganization. I will test emails to make sure subject lines are not empty.