New faceting search algorithm

Used new algorithm and data structure of data. It makes conjunctive and disjunctive operations of sets thanks to optimized Bitmap.

It makes faceted search 5-20x faster. Realtime searching for thousands items should take 5-10 ms.
Even for 100K items less than 100 ms

itemsjs.min.js size: 133 KB

What's Changed

• faceted search - improved algorithms by @cigolpl in #61

Full Changelog: v1.0.49...v2.0.0