Database: optimized hasOne reference invalidation
Database: refactored loading references
Database: ActiveRow::update() refetches data from database
Database: Selection::insert() returns IRow data fetched from database
Database: removed deprecated __set & __unset from ActiveRow, is is now read-only
Database: simplified for new read-only ActiveRow
Database: use IRow instead ActiveRow
Database: tests typo
Database: changed SqlLiteral::__construct(), parameters must be passed as array
Database: fixed inserting Selection [Closes #790]