Prevent ClassCastException when encountering ItemGroup of
non-TopLevelItem.

This is the case for instance when encountering a MavenModuleSet which
is ItemGroup<MavenModule>
[FIXED JENKINS-17030] Enable word breaking for job names
Explicitly turn of default escaping
[FIXED JENKINS-17774] Make not to copy a webapp directory every time for each tests.
Copying every time causes overwriting files in the webapp directory, and often causes errors in Windows.
This reverts JENKINS-12647(commit 7ae303f88191a540491a21484316d63dff775e21).
Various improvements from code reviews
Merge branch 'master' of https://github.com/jenkinsci/jenkins
Update changelog, should have been updated with original merge in to 1.515
Update Messages_es.properties

Correct spelling
[JENKINS-15652] Include directory in assertion messages so it is possible to tell which project is broken.
Lack of HTML escape made Javadoc misleading.
creating an RC branch
the trunk is toward 1.517-SNAPSHOT
Merge remote-tracking branch 'origin/master'
Merge pull request #783 from Johnbo/patch-1

Update Messages_es.properties
Merge pull request #767 from olivergondza/wbr_layout

[FIXED JENKINS-17030] Enable word breaking for job names.
[JENKINS-17030] Noting, fixing/adding @since, adding @Bug.
Merge pull request #774 from dnadolny/master

[JENKINS-17478] Various improvements from code reviews
[JENKINS-16301] Replace impl of getDigestOf with standard (Commons Codec) DigestUtils.md5Hex, for simplicity.
[JENKINS-16301] Use a buffered input stream to get somewhat better performance.
JUnit 4.