Generators

Created generators for job types:
- Synchronous
- Container aware
- Throttled
- Loner

Based on the [Controller generator on the Symfony 2.2 branch](https://github.com/sensio/SensioGeneratorBundle/blob/2.2/Generator/ControllerGenerator.php)

Note: The generators in master now extend from the [Generator](https://github.com/sensio/SensioGeneratorBundle/blob/master/Generator/Generator.php) class, which will allow to remove some code from the JobGenerator class when upgrading versions.