avoid System.out.println
Fix plugin for lazy loading.
Merge branch 'master' of https://github.com/jenkinsci/disk-usage-plugin

Conflicts:
	src/main/java/hudson/plugins/disk_usage/DiskUsageProperty.java
	src/test/java/hudson/plugins/disk_usage/integration/DiskUsageUtilTest.java
Merge branch 'upstream/master'