A simple layout calculator to make creating profiles easier

This implements a simple visual editor to calculate positions, width, and height values for presentation and presenter videos. It includes the ability to "snap to" a few custom aspect ratios. This should make creating custom video layout profiles significantly easier. It operates separately from the paella player, relying only on jQuery.

![screenshot-2014-11-17t14 50 59](https://cloud.githubusercontent.com/assets/3966/5076527/75f46cd4-6e69-11e4-9b21-42cdbc5f3119.png)