Feature: Product Metas

_This is still a work in progress (Control Panel updates are complete but new APIs need to be built out)._

This pull request adds the ability to define and attach custom product meta data. New Product Meta concepts have been added and the control panel's product configuration tool has been significantly updated.

__Concepts Summary__
 * __Product Meta:__ A meta name definition (e.g., Size)
 * __Product Meta Option:__ A meta value definition (e.g., Size: Large)
 * __Product Option Meta:__ A meta option attached to a product option (e.g., Luxury Touch Polo -> Size: Large)

Each Product Meta can have one or more Meta Options. And there is a many-to-many relationship between Meta Options and Product Options.

__Control Panel Summary__
The Product control panel pages now include a left nav, similar to the Customer management pages.

![products](https://cloud.githubusercontent.com/assets/1553251/5024313/1c08aad0-6ace-11e4-871d-983a7887f1c8.png)

![metas](https://cloud.githubusercontent.com/assets/1553251/5024317/2472dd3a-6ace-11e4-9a74-995d46046b4f.png)

![meta-options](https://cloud.githubusercontent.com/assets/1553251/5024318/26aa4b6a-6ace-11e4-9a8e-a21616e1e389.png)

![product-metas](https://cloud.githubusercontent.com/assets/1553251/5024320/29957098-6ace-11e4-9472-a23aaf701e7f.png)