Fix WebDAV auth for session authentication only

also show message for empty display name if change of it isn't allowed

\Sabre\DAV\Auth\Backend\AbstractBasic::authenticate was only calling \OC_Connector_Sabre_Auth::validateUserPass when the response of \Sabre\HTTP\BasicAuth::getUserPass was not null.

However, there is a case where the value can be null and the user could be authenticated anyways: The authentication via ownCloud web-interface and then accessing WebDAV resources. This was not possible anymore with this patch because it never reached the code path in this scenario.

This patchs allows authenticating with a session without isDavAuthenticated value stored (this is for ugly WebDAV clients that send the cookie in any case) and thus the functionality should work again.

To test this go to the admin settings and test if the WebDAV check works fine. Furthermore all the usual stuff (WebDAV / Shibboleth / etc...) needs testing as well.

Prioritise Basic Auth header over Cookie

set MySQL autocommit on connection setup

Fix chunked query for tags + unit test

fix typo of blog -> changed to block

check if mimetype is set - fixes #13452

* fixes #13460

Drop the hide and show of new users in user list

Remove stripslashes() from newfolder.php

[trashbin] replace hook with storage wrapper

Fix getItemSharedWithUser for groups

LDAP Wizared: update user or group count only, when the multiselect is closed

Fix filtering for users when $gid is empty

Reuse the array key of mimetypes

fix typo - caused by 3d997e8c

Fix exif orientation for flipped images

fixes #13363

Links:
 * http://www.daveperrett.com/articles/2012/07/28/exif-orientation-handling-is-a-ghetto/
 * Example data: https://github.com/recurser/exif-orientation-examples

fix safari rename button positioning #11348

fix unlocalized favorites browser title and alttext

Previously when $gid was empty the users were not filtered at all. Rendering the search function in the user management pretty useless.

Fixes itself

Skip stray part files during initial encryption

This function is called a lot of times and was really slow before due to not reusing the same array.

Previously when it was called 500'000 times it took about 2seconds, now we're down to 0.2 seconds on my local machine.

Ref https://github.com/owncloud/core/issues/13434