Shipping helper/USPS/UPS dimensions and other fixes.

As promised, here are the modifications needed in order for the USPS and UPS modules to get package dimensions to calculate shipping. The packages dimensions were not set, so each module was rounding each package dimension to 1 in. I added some filters and class properties to allow for future shipment packaging optimization. If you require any information, please don’t hesitate to ask.

![pll20131216_5](https://f.cloud.github.com/assets/5473636/1795868/1121eca6-6a40-11e3-87a8-d4494b306258.jpg)