Issue #475 - absolute time-range for a dashboard from the URL

Issue #475 - absolute time-range for a dashboard can be passed using "from" and "until" GET-parameters in the URL (http://graphite/?from=2013-10-27T22:00:00&until=2013-10-27T23:00:00#cpu - to open the CPU dashboard in the given time range). Format of the time range boundaries is "YYYY-MM-DDThh:mm:ss"