ezmultiupload 6.1.3: stricter access and limit checks

The upload service and the ZIP importer check access and limits more strictly (pull request #5), with two further checks of the location actions.

Upload service

• A location or item the user cannot read is answered like one that does not exist: no name, no path, the same message (check, uploadTarget(), Move, Add location, Remove and the upload page).
• Paths, the location picker's path and an uploaded item's list of locations leave out the locations the user cannot read.
• Without a form token in use, a request is taken only when the browser says it comes from the same origin (Sec-Fetch-Site, or the Origin header where no Sec-Fetch-Site is sent).
• Remove asks, as the kernel's remove view does, whether every location of the item may be removed with everything below it (can_remove_all), and refuses an item with items below it.
• Move, Add location and Remove refuse an item with a top-level location, and the root node as a target.

ZIP importer

• ZIP files inside an archive are unpacked within MaxTotalSize together, over all levels; past MaxEntries the walk stops on every level.
• extract() removes its own directory when it fails; a directory left behind by a request that died is removed by a later import after an hour.

Tests: tests/expMultiuploadServiceAccessTest.php (new, 7 cases) and tests/expMultiuploadZipImporterTest.php (18 cases), both without the kernel. Changelog: doc/changelog.md.