Added connection abstract
- Added Connection abstract class in concrete classes.
- Removed redundant properties/methods (kept type hinted elements)
- Enforced interface contract method return type for several transactions methods.
- Used accessors instead of properties in transactions methods
Made getResource() more consistent between Drivers, getResource() now
tries to connect if not connected in all the drivers.
Added unit tests for transaction support.
@return Connection => @return self
PSR-1 fix
PSR fix
Moved back driverName property to pdo
Added connection stub