Feature/lws 88 boosting

[kwahlin]

Boost same fields in Libris Search as in the cataloging.

• Code adapted from mainly ESQueryLensBoost.groovy and some parts from ESQuery.groovy. Should produce exactly the same boosted fields.
• Set _debug=esScore to include scores + explanation in the API response. Works with both the "old" query style (using q param) and the "new" (_q). Thought it might facilitate working with improved relevance.
• Use _boost for custom boosting, e.g. _boost=hasTitle.mainTitle^200,prefLabel^100....
• A bug was discovered in the existing code: When computing boosting from cards a field would not be boosted if another field containing the same nested subfield was already boosted. E.g. boosting publication.year would block production.year from being boosted. See fix: bdb3d08.

[jannistsiroyannis]

I wont claim to understand much of it, but I saw nothing obviously problematic!