Add option to sort data series before graphing

[aalpern]

From internal feedback:

When multiple queries return different metrics about the same set of hosts, there's no guarantee they'll be in the same order. This means that in a dashboard with multiple graphs about the same set of hosts, the same host may be represented by different colors in each graph.

Adding an option to sort the data series in a query by series key would ensure they match up (assuming your queries returns comparable series names).