Add new storage factory for distributed sessions
Add new storage factory for distributed sessions

Our default storage factory has always been QubitSessionStorage which extends
sfSessionStorage. In scenarios where AtoM is deployed across multiple nodes,
sessions musn't be stored locally. This commit adds QubitCacheSessionStorage,
which extends sfCacheSessionStorage.

Example (factories.yml):

prod:
  storage:
    session_name: symfony
    session_cookie_httponly: true
    session_cookie_secure: true
    cache:
      class: sfMemcacheClass
      param:
        ...

Surfrdan/atom,artefactual/atom,artefactual/atom,kyfr59/atom-cg35,artefactual/binder,artefactual/atom,kyfr59/atom-cg35,artefactual/binder,artefactual/binder,CENDARI/atom,Surfrdan/atom,CENDARI/atom,artefactual/binder,kyfr59/atom-cg35,Surfrdan/atom,CENDARI/atom