use gedmo for soft delete & created/updated timestamps
use gedmo soft deleteable & timestampable from now on
changelog & small additions
changelog / upgrade doc
Merge branch 'feature/gedmo-soft-delete' into feature/folder-tree

* feature/gedmo-soft-delete:
  changelog / upgrade doc
  changelog & small additions
  use gedmo soft deleteable & timestampable from now on
  use gedmo for soft delete & created/updated timestamps

Conflicts:
	Entity/Folder.php
	Form/FolderType.php
	Repository/FolderRepository.php