Fix EZP-22400: Use FOSHttpCacheBundle

> https://jira.ez.no/browse/EZP-22400

This PR adds support of FOSHttpCacheBundle and replaces eZ custom logic by FOSHttpCache

Depends on:
* https://github.com/FriendsOfSymfony/FOSHttpCache/pull/128 (merged)
* https://github.com/FriendsOfSymfony/FOSHttpCacheBundle/pull/152

## TODO
* [x] Implement HTTP cache invalidation
* [x] Make user hash use FOSHttpCache *User Context*
* [x] Tests
and actually, Travis is already installing 3.0.2