Fix EZP-22928: Embed inline image are always seen as inline in Online Editor
Fix EZP-22554: Email error when registering a user
Fix EZP-22915: Clearing caches fail if cache folder is symlinked
Merge pull request #978 from ezsystems/ezp-22554-user_register_email

Fix EZP-22554: Email error when registering a user
Merge pull request #981 from ezsystems/fix_EZP-22915_recusirveDeleteSymlink

Fix EZP-22915: Clearing caches fail if cache folder is symlinked
Merge pull request #977 from ezsystems/ezp-22928_embed-inline_inline

Fix EZP-22928: Embed inline image are always seen as inline in Online Editor
fix:EZP-22917 when cache removal fails, no message is displayed
Merge pull request #979 from pbras/ezp-22917_cache_removal_log_errors

fix:EZP-22917 when cache removal fails, no message is displayed
EZP-22966: Extracted DFS DFSBackend Interface

It is extracted from the current eZDFSFileHandlerDFSBackend,
that now implements it.

dfscleanup.php had to be modified as it was using quite a lot of
the eZDFSFileHandlerDFSBackend internals. New methods were created
in the interface to account for those changes.
Merge pull request #984 from ezsystems/EZP-22966-dfsbackend_interface

Extracted eZDFSFileHandlerDFSBackendInterface
EZP-22960: Made DFS FS backend configurable

A new INI setting, eZDFSClusteringSettings.DFSBackend, is introduced.
It sets the backend class used by DFS.

The backend instance is provided by eZDFSFileHandlerBackendFactory.

If a backend implements eZDFSFileHandlerFactoryDFSBackendInterface,
it will be constructed using a 'factory()' static method. If it doesn't,
and instance will be created using 'new'.