Autoloader fix

Lock jobs while executing them, to allow multiple executors to run in…

Add interface methods for permission check for system tags

For setting/getting system tag groups

Whenever the server returns true for the can-assign Webdav property of
a system tag, it means the current user is allowed to assign,
regardless of the value of user-assignable.

This commit brings the proper logic to the web UI to make it possible
for users to assign when they have the permission.

Whenever a user is not an admin, a tag is visible but not
user-assignable, check whether the user is a member of the allowed
groups.

Added systemtag to group mapping table.
Added methods in ISystemTagManager to get/set the group mappings.

Instead of checking for admin perm, use interface method
canUserAssignTag and canUserSeeTag to check for permissions.
Allows for more flexible implementation.

Add scrolling when dragging files. Fixes #12329

* Move a-b to PSR-4

* Move c-d to PSR-4

* Move e+g to PSR-4

* Move h-l to PSR-4

* Move m-r to PSR-4

* Move s-u to PSR-4

* Move files/ to PSR-4

* Move remaining tests to PSR-4

* Remove Test\ from old autoloader

add --unscanned option to files:scan to triger a background scan

Fix autoloader for Test* files

Load external storage backends/auth mechanisms lazily

Move \OCP to PSR-4