Optimise full text search query builder for deep category hierarchies

Deep category hierarchies with "search in sub categories" option result in Lucene error boolean clauses exceed 1024.

Need to optimise how we manage search in subcategories by storing full parent tree structure and then have single clause for including current category. Since we can only pass List<Longs> we can pass negative PK to indicate "search in sub categories". The challenge is to traverse the parent tree with category links included