Move symfony cache component

Fix #170, Replace #177

Depends on https://github.com/FriendsOfSymfony/FOSHttpCache/pull/145

*TODO*
* [x] Wrap up https://github.com/FriendsOfSymfony/FOSHttpCache/pull/145 and up the required version in composer.json
* [x] Documentation (see also #178 but note that things changed since then)
It seems superfluous to me - if you inject the ED then you can talk to the ED about ED things. If we provide proxy methods it just allows 2 ways to do the same thing and obfuscates what is really going on and distracts the class from its true intentions.

Injecting the ED in the Bundle doesn't add any overhead and you could reuse the Symfony ED which would make it straight forward to users as they only ever have to talk to a single ED.