Add access grant check on backend side.

[corentin-soriano]

There are currently places in php where access grants on items are not properly checked.
A malicious user can edit the request before sending it to the server or edit the DOM with the debug console to bypass restrictions.

Now:

• User can't move item from ND folder (as it removes item from source folder).
• User can't move item on any folder without W access (ex: personal folder of an other user).
• User can't remove item in ND folder by removing hidden class on .form-item-delete.

Using the code from check_current_access_rights query to create function getCurrentAccessRights().
Returns true instead of null which was confusing.