[master] stats improvements

[master] stats improvements

3700.	[func]		Allow access to subgroups of XML statistics via
			special URLs http://<server>:<port>/xml/v3/server,
			/zones, /net, /tasks, /mem, and /status.  [RT #35115]

3699.	[bug]		Improvements to statistics channel XSL stylesheet:
			the stylesheet can now be cached by the browser;
			section headers are omitted from the stats display
			when there is no data in those sections to be
			displayed; counters are now right-justified for
			easier readability. [RT #35117]