Improve backend lookup in additional results block and zero results page.

* 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.
Fallback on sorting by location/library code if there is no configured name.
Update home page layout.
remove top level class references
Merge pull request #707 from sul-dlss/location-sort-bug

Fallback on sorting by location/library code if there is no configured name
Merge pull request #713 from sul-dlss/inst-fix

remove top level class references
Merge pull request #710 from sul-dlss/home-page-layout

Update home page layout.
Merge pull request #706 from sul-dlss/diff-results

Improve backend lookup in additional results block and zero results page
Add public_note and callnumber_type methods to the callnumber class.

Prerequisite for #469 and #566.