More Like This Class Structure Refactor

Currently the MoreLikeThis is a giant monolithic class, difficult to maintain.
Scope of this issue is to refactor the code, separating responsibilities of the main components and funcitonality :

• MoreLikeThis facade - the entry point
• MoreLikeThisParams - the huge set of params and defaults provided for the More Like This
• Interesting Terms Retriever - given a document in input this component has the responsibility of identifying interesting terms
• Term Scorer - given a term with document stats and collection stats, this module has the responsibility to score the term
• Query Builder - given a set of params and interesting terms, this component has the responsibility to build the Lucene query