New colour-picker for setting plot colours!

Added a colour-picker for setting plot colours.

It does not work in firefox, since apparently firefox doesn't support the HTML5 colour picker yet. It does gracefully degrade to a text-box, though, so it's *usable*, just not nice and pretty.

![colour picker 1](https://f.cloud.github.com/assets/1401239/2195218/a8b15ae8-9899-11e3-8e9a-ced7197d3be0.png)


![colour picker 2](https://f.cloud.github.com/assets/1401239/2195217/a5945f54-9899-11e3-937d-0d96c0fd710d.png)