Add SentryConsoleErrorHandler for handling Console Errors

In relation to https://github.com/Sandreu/cake-sentry/issues/4.

The following code needs to be placed in "bootstrap.php", right after the CakePlugin('Sentry') has been loaded.

```php
  App::uses('SentryConsoleErrorHandler', 'Sentry.Lib');

  Configure::write('Error', array(
    'handler' => 'SentryErrorHandler::handleError',
    'consoleHandler' => [new SentryConsoleErrorHandler(), 'handleError'],
    'level' => E_ALL & ~E_DEPRECATED,
    'trace' => true
  ));

  Configure::write('Exception', array(
    'handler' => 'SentryErrorHandler::handleException',
    'consoleHandler' => [new SentryConsoleErrorHandler(), 'handleException'],
    'renderer' => 'ExceptionRenderer',
    'log' => true
  ));
```