* update iresearch from upstream
* adjust tfidf/bm25 to original behaviour
* update iresearch from upstream
* fix compilation issues
* reduce number of virtual calls
* upgrade iresearch from upstream
* add js test
* issue 511.5: remove cid from IResearchPrimaryKey since iresearch data-stores are per-collction, minr code cleanup
* get rid of CID field in a document
* make ArangoSearch PK encoding/decoding logic explicit
* issue 506.2: add optimization to not reexecute a primary-key filter if a match was already found
* backport: explicitly check type of instance of the primary-key filter
* backport: return non-null prepared filter and convert check to assert
* issue 153: ensure views are dropped in Agency when database is dropped in cluster, minor fixes
* backport: add test to ensure views are dropped when database is dropped from plan, fix some issues in ClusterInfo
* optimize primary key lookups in ArangoSearch
* fix test
* Add JS tests
* temporary comment optimizations
* refactor arangosearch pks
* minor refactoring
* store PK as BigEndian since it leads to more compact index representation
* force iresearch to not to use libbfd
* fix tests