Feature/graphs

Here's the graphing stuff. I ended up making it so the front-end graphing JavaScript (no CoffeeScript needed) is flexible and doesn't require changing just to add a new graph. All that's needed is appending a "graph definition", which is just a dictionary with the title and a list of the series. The graphs will optionally auto-refresh every 10 seconds, and the viewing range can be varied between the previous 10 minutes, 30 minutes, 1 hour, and 2 hours.

There are also sample graph and annotation snippets that can be enabled to check the styling. Keeping unchanging time-based data visible in a graph based on "now" gets trickier and trickier as time goes on.