Merge branch 'security' into security-stable-1.580

Conflicts:
	core/src/main/java/hudson/model/DownloadService.java
	core/src/main/java/hudson/model/UpdateSite.java
	core/src/main/java/jenkins/model/DownloadSettings.java
	core/src/main/resources/hudson/model/UpdateCenter/PageDecoratorImpl/footer.jelly
	core/src/main/resources/jenkins/model/DownloadSettings/config.groovy
	core/src/main/resources/jenkins/model/DownloadSettings/help-useBrowser.html
	test/src/test/java/hudson/model/DownloadServiceTest.java