[Bug 857148] Improve rickshaw_utils.

This is basically a rewrite of `k.rickshaw.makeGraph` into `k.Graph`, a more powerful class to make graphs.

- Merge most of the logic of the history chart into `rickshaw_utils.js`
    * Series colors
    * Choosing series sets
    * Slider controls
    * Timelines (annotations).
- Make `rickshaw_utils.js`'s primary export a constructor instead of a simple class.
- Some graph controls are generated automatically, instead of done in the DOM.
- Feature toggling is done in JS instead of by presence of certain DOM nodes.

r?