dashboard fixes and enhancement

* better support for reverse-proxies
* fixing a locale-related bug when ids are > 1000
* add support for passing graphite parameters to all graphs at once in dashboard url (e.g. from=-2d, yMin=0 or bgcolor=blue)
* add usual timeframe links ("last day", "last 2 weeks", etc.) on top of dashboards to make timeframe switch easier
* add clone links for graphs and lines