Renamed RRDView to MetricMixin and removed methods unused outside of rrdplugins and reports
removed rrdtool from version
removed migrates that imported rrdtool
removed zenrender as well as RenderServer and RenderConfig
removed zenrrdcached
removed unused methods from PerformanceServer as well as added returnset as an option for metricfacade getValues
added back RenderURLUtilContext
updated unit test
Merge pull request #20 from zenoss/feature/metricmixin

Rename RRDVIew to MetricMixin, remove RenderServer, zenrender and RenderConfig. Updated core PerformanceServer to remove unused methods