no-jira: add alias in course xstream configuration of AttributeEndswithOperator for backwards compatibility with OLAT 7.8

OO-2008: check the length of selections, show a validation error if the user name column is not selected

OO-1935: remove the mail.smtp.from property set in the mail session, slight changes in forward email from to not have no-reply mail address in the reply field

OO-1985: merge the forums of a course element if there are several properties saved on the database and remove them minus one

OO-1980: better check model boundaries and deselect the table multi selection if the search arguments have changed

OO-1979: check if the selected page for the single page course element is really a file and not a directory