Fixing layout in product admin interface

I always have the problem that the admin interface on the products edit page looks a bit broken. This is because the fields for the form did not have the correct containers and classes. I fixed this. See the attached screen shots for comparison.
![screen shot 2013-08-29 at 16 15 14](https://f.cloud.github.com/assets/878221/1050178/9236b59a-10b5-11e3-970f-753dda08403a.png)
![screen shot 2013-08-29 at 16 17 27](https://f.cloud.github.com/assets/878221/1050192/c1b98f18-10b5-11e3-8ae9-d2469c61554e.png)