Affiliation search improvements

[lizkrznarich]

• Check for exact matches first
• De-prioritize acronym search results
• Don't mark multiple results as chosen = True
• Exclude search strings that match specific common phrases, country names, country codes and city names
• String special chars (except &) from search strings
• Include full entered string as a search term in all searches
• Generate fewer search substrings
• Only return results with a score of >= .5