Improve shipping admin

![google chromescreensnapz021](https://f.cloud.github.com/assets/1079437/457344/b34c25a4-b394-11e2-82f6-01c010460637.png)
![google chromescreensnapz022](https://f.cloud.github.com/assets/1079437/457343/b34e798a-b394-11e2-96cb-21d84c673336.png)

More screenshots: http://imgur.com/a/faHjB

Done to make Shipping reflect positive changes made recently in Payment Gateways. 

* Lots of bringing code up to coding standards in shipping modules.
* Rewriting superfluous messages, improving existing messages.
* IMPROVE ALL THE LAYOUTS!

You would be surprise how many snippets of code I replaced with ```checked()```, ```selected()```, and even ```disabled()```. The person who put those in WordPress is a genius.