better solution

The web UI now uses for PUT uploads which aren't restricted by PHP's
upload_max_filesize and post_max_size

Signed-off-by: Lukas Reschke <lukas@statuscode.ch>

- uses PUT method with jquery.fileupload for regular and public file
  lists
- for IE and browsers that don't support it, use POST with iframe
  transport
- implemented Sabre plugin to handle iframe transport and redirect the
  embedded PUT request to the proper handler
- added RFC5995 POST to file collection with "add-member" property to
  make it possible to auto-rename conflicting file names
- remove obsolete ajax/upload.php and obsolete ajax routes

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

Hidden files (dot files) are now always rendered in the DOM to make
sure that all file operations and selection still work as expected.

Their visibility is now toggled on CSS level.

* divides the area where the scroll should be triggered by 2
* uses the minimum value of the above and 300

The background job will now be executed in chunks of 500 users all 10 minutes.

The public page now uses the public.php/webdav endpoint.

Also enabled more file operations like rename, move, delete and create
folder from the public page, which are now all possible thanks to the
public.php/webdav endpoint.

- Clicking a file row or selecting it will open the sidebar.
- When sidebar is open, its contents update with the last selection.
- Dragging doesn't open the sidebar but does update its contents if it was
open already.
- Switching folders closes the sidebar.
- Close sidebar when highlighted file got deleted/removed from list

* ref #12877

* removed the setDefault call because then it will always be
  reshown
  * was added with ba475d48
* fixes #18208

* getstoragestats.php returns now the owner and it's display name
* show proper storage stats notifications for shared folders

Since the thumbnail is now in a div, the code that tries to change the
thumbnail have been adapted here as well.

Added namespaces so that JSDoc can find them.
Fixed a few warnings.
Improved some comments.

When dropping files onto a read-only folder, a notification
is now shown instead of attempting to upload.

This for both the drag for upload and drag from inside the file list
cases.