Fixed outstanding uses in core of deprecations from #1135 & #1138.
Merge branch 'master' into DownloadSettings-JENKINS-19081

Conflicts:
	core/src/main/java/hudson/model/DownloadService.java
	core/src/main/java/hudson/model/UpdateSite.java
Testing the loadJSON method directly to make sure various JSONP formats are handled.
Deleting failing test updateDirectlyWithHtml.
loadJSON does not support parsing HTML.
Nor should it need to, since UC URLs are supposed to be to the JSONP file.
The .html extension is added automatically by downloadService when postBack is supported.