Multi database merged and updated (#5140)

* Update Db.php to manage multi database

* Update Db.php

* Update Db.php

* Update SqliteDbTest.php

* Update Db.php

* Update Db.php

* Update SqliteDbTest.php

* Update Db.php

* Update SqliteDbTest.php

* Update Db.php

* Update Db.php

* Update SqliteDbTest.php

* Update Db.php

* Update public function to protected function

* Add doc for amConnectedToDatabase

* Add deprecate on magic get method

* Add example for multi-databases

* Removed deprecated driver

* Update Db.php

* Merge branch 'multi-db' of https://github.com/eXorus/Codeception into eXorus-multi-db

# Conflicts:
#	src/Codeception/Module/Db.php

* small docs patch

Author: DavertMik