support >1 ajax requests per graph, to avoid http uri too large
support >1 ajax requests per graph, to avoid http uri too large

build_graphite_url():
* with many targets, don't yield a long uri that would get aborted.
  (414 Request-URI Too Large)
  instead always return a list of N uri's based on given limit.
* only properly supported for flot; not for png and rickshaw

vimeo/timeserieswidget,vimeo/timeserieswidget