Composer: added StofDoctrineExtensionsBundle
AppKernel: registered StofDoctrineExtensionBundle
App: register sluggable service + store services in separate file
UserBundle: added slug to the group entity
UserBundle: implemented slug on every view
Upgrade Symfony 2.5 > 2.6
UserBundle GroupController: bugfix name > slug
Config: configured form theme bootstrap
UserBundle Backend: refactored new group form
UserBundle: correct page titles on every template
UserBundle Backend: edit an existing group
UserBundle Backend: link to group edit page