Used xmllint --format

Noticed via failure in BuildCommandTest.testConsoleOutput.
https://github.com/jenkinsci/jenkins/pull/522

Note that http://netbeans.org/bugzilla/show_bug.cgi?id=197335 displays this incorrectly.

Rather than patching configure.jelly, safer and clearer to directly adjust ToolInstallation/global.jelly.

Fixed a problem in actually making concurrent builds work.

This prevents the section title from getting hidden by the breadcrumb
bar.