Reimplement SQL search engine
Reimplment SQL-based search engine (aka SqlSearch) with the following objectives:
1. Make code comprehensible, maintainable and testable
2. Fully implement support for NOT queries and +/- operators.
3. Implement support for wildcards anywhere in a search term (not just training); implement support for the "?" wildcard.
4. Fully support [BLANK] and [SET] queries
Please remember to fix also the multiterm search (I sent you an email time ago).