Improve Redirect Configuration meta box field arrangement

Resolves #13.

- Split various configuration options into separate meta boxes
- Added lots of inline documentation to help novice site owners

@jaswsinc A code review, some testing, and any feedback would be appreciated. :) 

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![2014-09-13_20-52-59](https://cloud.githubusercontent.com/assets/53005/4262561/8e04918e-3ba9-11e4-89f0-f607748e5abb.png)
![2014-09-13_20-53-13](https://cloud.githubusercontent.com/assets/53005/4262562/8fba543c-3ba9-11e4-8f10-c7bcac7cafd4.png)