Add Read/Write Connections and sqlite/pgsql/sqlsrv Support

- Add compatibility support for [Database Read/Write Connections](http://laravel.com/docs/database#read-write-connections) which was added in Laravel 4.1 ([changelog](http://laravel.com/docs/releases#laravel-4.1])).
- If db config specifies read/write params a Doctrine [MasterSlaveConnection](http://www.doctrine-project.org/api/dbal/2.3/class-Doctrine.DBAL.Connections.MasterSlaveConnection.html) will be created instead.
- Add support for all other Laravel supported databases; SQLite, PostgreSQL and SQL Server.
- Fix ignoring `port` config param not allowing user's to specify a custom mysql port.

**Implementation notes:**
I tried to mimic the same way Laravel detects a Read/Write Connection:
- Checking if Laravel's read/write connection is turned on is done by looking for 'read' param, the same as in Laravel's code [here](https://github.com/laravel/framework/blob/4.2/src/Illuminate/Database/Connectors/ConnectionFactory.php#L41).
- Getting `$writeConfig` and `$readConfig` is done the same as in Laravel's code [here](https://github.com/laravel/framework/blob/4.2/src/Illuminate/Database/Connectors/ConnectionFactory.php#L142).