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

---
![image](https://cloud.githubusercontent.com/assets/302258/3741087/454808d4-175c-11e4-8eba-1b18c22dc9ad.png)

@jkeck `.strip.blank?` check is from the earlier version of the file. Assuming it was added for a reason, I left it unchanged. Let me change it to `.present?`, do some tests and update the PR