Implement ability to exclude search terms from a search

[sonofmun]

Possiblities:

• implement regex search
  • The problem here is that it is difficult for the user
• implement another search box where excluded terms are put
  • This makes the advanced search screen more complex
  • It would also search the whole document for the term and thus if burg but not burgund were searched, even a document with burgus would not be found if it also had burgundus
• Allow user to right click on a term in the search results and run a new search excluding this term
  • How would you let the user know that this is a possibility
  • And it might also not find any documents with the excluded term even if the desired term is also in the document

[sonofmun]

Implemented a combination of the first and second options using ES regex capabilities in #573