[FIXED JENKINS-24119] Fixed icon src path generation

For icons not defined in the IconSet
Use IconSpec.getIconClassName() instead of Action.getIconFileName() where possible [JENKINS-24170]
Display thread associated with ThisIsHowItsLoaded when logging at FINEST.
Some loggers may show the thread name anyway, but /log/* in the UI at least does not.
And recent versions of Jenkins are being improved to capture lots of context in the thread name;
an unreleased improvement in Stapler includes the Jelly views being rendered.
Simplifying test to use JenkinsRule.assertLogContains.
f43a450c31d3875e72defa8400c6ada43bfc3ad0 addendum: during migration, if nothing else is being fingerprinted besides archived artifacts, then there is no reason to keep the separate fingerprint publisher at all.
[FIXED JENKINS-23027] Added Launcher.ProcStarter.quiet option.
[FIXED JENKINS-24181] Status icon not showing in the project view when "it" is not a BallColor
Merge branch 'master' of git://github.com/jenkinsci/jenkins
Fix typo in test name
[maven-release-plugin] prepare release jenkins-1.575
[maven-release-plugin] prepare for next development iteration
updated changelog for release
updated changelog as a part of the release
merged back the RC branch
creating an RC branch
the trunk is toward 1.577-SNAPSHOT
Merge branch 'master' into BuildStep-Job