Email Java Delegate should support attaching multiple files

[wwelling]

This can be accomplished by affording a comma separated list of file paths for attachmentPath and refactor it to attachmentPaths or add as an additional property and provide backward compatibility. The later would require deprecating the first and make for much more changes to take place. I suggest just making the refactor in mod-workflow, mod-camunda, and fw-registry before we have a release approved by FOLIO.