Adds side navigation in record view

Closes #374 

* Enables side navigation bar when record view page has scroll bar (for MARC and MODS objects)

Moved all repeating ids and icon tags to `searchworks.en.yml` for ease of maintenance

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![image](https://cloud.githubusercontent.com/assets/302258/3741087/454808d4-175c-11e4-8eba-1b18c22dc9ad.png)

@jchristo4 why is it that we're using `.strip.blank?` here instead of `.present?` like everywhere else?