override only mssql and sqlite QueryBuilder; throw an exception for composite in condition with a subquery

ensure PDO instance has been created at this point

Fixes #4644: Added `\yii\db\Schema::createColumnSchema()` to be able to customize column schema used

one method for fetching data and one for sending to db.

fixes #2287

fixes #3559

fixed some issues with schema detection

fixes #3220

This is a porting from yii framework version 1.
I need it to run functional tests with fixtures.

issue #2852

Fixes #2571: Fixed the bug that batchInsert will fail for SQLite if the values contain null or boolean false;
Fixes #2683: Fixed the bug that batchInsert will fail for MySQL if the values contain boolean false.

Improved `QueryBuilder::buildLimit()` to support big numbers