[WIP] Second-level cache configuration

This patch add support  for second-level cache https://github.com/doctrine/doctrine2/pull/808

Please notice that changes made in ``DoctrineExtension#loadCacheDriver`` should be moved to Symfony Bridge once we finish the work here...


![screen shot 2013-10-31 at 4 57 10 pm](https://f.cloud.github.com/assets/588172/1449808/288202bc-426f-11e3-93c4-26a7029f5842.png)

![screen shot 2013-10-31 at 4 57 30 pm](https://f.cloud.github.com/assets/588172/1449810/2ba6250e-426f-11e3-8c5f-bfcbef501610.png)


Cheers