[Form] Add magic getter method support to Entities

When using Symfony Forms, it permits the implementation of magic getter methods in those Entities by using the `__call` magic method.

It basically allows one to do the following in an Entity:

    public function __call($method, $arguments) {
        if (preg_match('/^(get|is|has)([A-Z].*)$/', $method, $matches)) {
            return $this->{lcfirst($matches[2])};
        }
        throw new \Exception(sprintf(
            'Method does not exist for class "%s".', get_class($this)
        ));
    }