Moves views menubar to header and other fixes


* Creates image viewer only header and moves count, views list and full-screen control to it
* Fixes image alignment issues in gallery view
* Fixes image heights in horizontal view to accommodate image labels
* Enhancements to full-screen view

![image](https://cloud.githubusercontent.com/assets/302258/5137220/fd6aadcc-70e9-11e4-8ab6-576698299bd8.png)
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![image](https://cloud.githubusercontent.com/assets/302258/5137320/7a5c3dea-70eb-11e4-9aa3-2990a80699c7.png)
![image](https://cloud.githubusercontent.com/assets/302258/5137322/87cd4050-70eb-11e4-8fe4-f804c140edf9.png)
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![image](https://cloud.githubusercontent.com/assets/302258/5137333/b74dd83a-70eb-11e4-842d-341815587e4f.png)
![image](https://cloud.githubusercontent.com/assets/302258/5137338/c8b63b08-70eb-11e4-875b-fdb20d46613c.png)

Image count has been moved from `common_viewer.rb` to image viewer plugin. Count is updated after image viewer (and its AJAX calls) are rendered. This test times out before image viewer is rendered.