Instanciate only if needed
Allow $phpSelf to be identical to $index
Fix EZP-22913: prevent exponential growth in number of queries when removing image alias attributes
EZP-22985: Add node assignments when handling local files
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.
Unneeded param in window.ScrollTo call in admin interface class edit template
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'.
Merge pull request #993 from ezsystems/EZP-22960-configurable_dfs_backend

EZP-22960: Made DFS FS backend configurable
Merge pull request #988 from jeromegamez/EZP-22982_to_slash_or_not_to_slash

EZP-22982: Allow $phpSelf to be identical to $index
Merge pull request #992 from crevillo/class-edit-window-scrollTo-bad-param

Unneeded param in window.ScrollTo call in admin interface class edit tem...
Fix EZP-22923: ezcontentobject_link table not cleared when a relations attribute is deleted from a class
Merge pull request #987 from ezsystems/ezp-22923-delete_attribute_links

Fix EZP-22923: ezcontentobject_link table not cleared when a relations a...
Fixed minor error in DFSBackend factory
Merge pull request #990 from jeromegamez/EZP-22985_fixed_relationships_<3

EZP-22546: Fixing file uploads with the ezpRelationListAjaxUploader
Removed obsolete deprecated method
Merge pull request #982 from joaoinacio/EZP-22913_removealiases_queries

Fix EZP-22913: prevent exponential query growth when removing image alias
Added legacy extensions to composer.json

- Ensure that setup wizard enables them.
- Ensure only kernel tests are run by Travis
Bumped master to 5.4.0alpha1
Merge pull request #991 from ezsystems/bump_5.4.0_alpha1

Bumped master to 5.4.0alpha1