added nonNegativeDerivative function

simplified a lot of the time series data manipulation prior to handing it to flot, kibana used a lot of code to sort and make sure all time points needed had values, this is not needed for graphite time series data. Fixes som strange issues with "null point mode" and inconsistent rendering between graphite and grafana flot,

basic authentication added for elasticsearch

fixed missing module for 'moment' and jslint missing semi colon

fixes 'derivate' function name - correct name is 'derivative'

Added new config setting timezoneOffset, usefull when your graphite server is on a different timezone thant your users browsers. This is not optimal (for example if your users have different timezones) can be improved by finding a way to query the timezone different between browser and graphite server. Or fix so that the &tz graphite parameter works for json, then all absolute filters can use UTC time.  #31

Update graphiteSrv.js

Fixed graphite import to include all graphs in a dashboard.