Fixed [JENKINS-21101] & [JENKINS-20977]

Pull request for the following issues
[JENKINS-21101]
[JENKINS-20977]

1 - Modified the ChangeLogWrapper to Extend ChangeLogSet<Entry> so that any plugin using the items property to get the entries will function correctly.
2 - Escaped the XML prior to writing to the sub-log section, and un-escaped it prior to writing it to the temp changelog