Cache unsubmitted comments

[CSchmitz81]

Cache unsubmitted element comments. Currently if you close an element details and reopen the same element it keeps the same comment, but if you open details for a different element and go back to the original the comment text is cleared. Instead, it would be best if the comment text is retained. It's fine to just keep the text during the current session, so it can be stored into a temporary field in the element and reloaded when the element details are loaded. Be sure not to retain text after it's submitted.