EZP-22400: Added friendsofsymfony/http-cache-bundle dependency
EZP-22400: Added FOSPurgeClient
EZP-22400: Deprecated Multiple/Single purge clients and associated config
EZP-22400: Undeprecate multiple_http and single_http, but considers them as just "http"

"http" purger is now always using FOSPurgeClient and sends a unique BAN request for all locations to purge.
Such BAN requests are supported by Symfony internal reverse proxy, via LocationAwareStore.
EZP-22400: FOSPurgeClient now only supports BAN request
EZP-22400: Make LocalPurgeClient the default one back.
EZP-22400: Implemented a factory to build Varnish proxy client

This makes it possible to merge purge servers defined in eZ SiteAccess aware config with the one defined at FOSHttpCacheBundle levels
EZP-22400: Fixed some tests
EZP-22400: Removed obsolete HttpBasedPurgeClientTest
EZP-22400: Added test for FOSPurgeClient
EZP-22400: Added tests for VarnishProxyClientFactory
EZP-22400: Added test for HttpCachePass
EZP-22400: Updated tests for LocationAwareStore
EZP-22400: Delegate user context hash generation to FOSHttpCacheBundle

Depends on:
* https://github.com/FriendsOfSymfony/FOSHttpCacheBundle/pull/152
* https://github.com/FriendsOfSymfony/FOSHttpCache/pull/128
EZP-22400: Fixed RoleContextProviderTest
EZP-22400: Fixed tests
EZP-22400: Use FrameworkExtraBundle 3.*
EZP-22400: Added BC doc
EZP-22400: Added specs on FOSHttpCache usage
Fixed CS and missing PHPDoc