2.3.0

• full support for working under Windows;
• added Driver::getConfig() method, removed Driver::$config property. This
  allows you to get the configuration values safely;
• fixed a bug for export and import executables with Postgres databases;
• before importing a sqlite backup, each table is dropped, rather than deleting
  the database file;
• added isWin() global function;
• tests can have onlyUnix or onlyWindows group.

Thanks to @swiffer for the valuable contribution in supporting Windows.