Adds Persistent URL link to both Collection and Work views. #540

[bwatson78]

1. catalog_controller.rb: ensures that the "id" key/value gets populated in view.
2. _find_this_item.html.erb: changes render call to the new custom partial listed below.
3. find_this_item.yml: includes id and it's label in fields for the presenter to digest.
4. _find_this_item_block.html.erb: copies from metadata block but adds logic that formats the PURL correctly.
5. spec*: adds test elements for the new metadata link.

[bwatson78]