Improve backend lookup in additional results block and zero results page

Closes #674 

* Don't show "Remove limit(s)" link unless there is a query (so we don't lead to an all results page).
* Don't show the additional results block on any page but the first page.
* Don't execute backend lookup until the link is in the viewport to minimize solr queries.
* Removed disabled Article search link.
* Only link to WorldCat/Library search when there is a query to search.

![backend-lookup](https://cloud.githubusercontent.com/assets/96776/3900255/febe14b6-2288-11e4-9c33-f2e8777571fb.gif)

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#### Search w/ filters
![search-w-filters](https://cloud.githubusercontent.com/assets/96776/3900257/10afcb24-2289-11e4-90ff-d8b3139ffa57.png)
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#### Search w/o filters
![search-wo-filters](https://cloud.githubusercontent.com/assets/96776/3900256/109ecf5e-2289-11e4-9be2-ee1502b37bf7.png)
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#### Search w/ stop-words
![search-w-stopwords](https://cloud.githubusercontent.com/assets/96776/3900258/10c261c6-2289-11e4-99f4-990c5faf76a4.png)
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#### Zero results w/ filters
![zero-results-w-filters](https://cloud.githubusercontent.com/assets/96776/3900259/10d13660-2289-11e4-9961-35eb7964cdf6.png)
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#### Zero results w/o filters
![zero-results-wo-filters](https://cloud.githubusercontent.com/assets/96776/3900260/10e705b2-2289-11e4-987c-56c650cd607c.png)