fix for gallery lightbox image sizes

- limiting gallery lightbox images to their original size or to the width of the window.
- removing nav arrow alignment as it causes the nav arrows to jump around when really they should stay in the same place


Before
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![image](https://f.cloud.github.com/assets/960919/2411672/1ba095e0-aaca-11e3-810b-1fa719c9f683.png)
After
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![image](https://f.cloud.github.com/assets/960919/2411679/2f5f1f34-aaca-11e3-9602-ff548d3102a9.png)