Campaign Shipment Form

Adds new helper variables to implement a Shipment Form on a campaign.

Creates Shipment Form modal on a campaign based on helper variable config.

Closes https://jira.dosomething.org/browse/DS-452.  Creates Shipments properly for non-shirt Shipment Items (Shirts need additional form elements for style and size, there are `@todo` comments for this, if we ever need to do that)

![screen shot 2014-10-03 at 3 08 45 pm](https://cloud.githubusercontent.com/assets/1236811/4511076/bca18bc8-4b30-11e4-81e4-013d66ebc49d.png)


Any reason in particular?  We use similar callbacks in other modules that use Form API...