Display "LC Subject" instead of "Lcsubject"

- Moves metadata-related I18n rules to more generic location
- Adds new class to centralize I18n pull of field label
- Uses central label algorithm on the search, show view, and ingest form
- Removes subject from search results per requirements
- Fixes faceting to use "lcsubject" field as "Topic"
Merge pull request #274 from OregonDigital/feature/fix-lcsh-ui

Display "LC Subject" instead of "Lcsubject"