Failing mysql master tests

Clean up AppFramework database layer

using Doctrine\DBAL\Connection::executeUpdate()

Show 404 page when accessing empty share URL

Return null when requesting tags for null user

Remove unused and deprecated Code

Message clean-up

Testplan:
- [ ] Without: Accessing `public.php?service=files&t=` throws an exception
- [ ] With: No exception thrown and 404 page displayed.

Fixes https://github.com/owncloud/core/issues/14231

The TagManager->load() now returns null if the user is not authenticated
instead of failing with an error.

Cleanup garbage collection for global file cache

Use getRemoteAddress which supports reverse proxies

Function is not used anymore anywhere in the code base: https://github.com/search?q=user%3Aowncloud+secureRNGAvailable&type=Code&utf8=%E2%9C%93

Add some PHPDocs

Add support for sftp custom port	

Get the real protocol behind several proxies

Fix bugs in ownCloud external storage

Better config cleanup in autotest.sh

Sabre Update to 2.1

Reasoning:
- a WebDAV server is not required to implement locking support
- WebDAV Locking is know to break the sync algorithm
- the current lock implementation is known to be broken (locks are not moved if a file is moved, locks on shared files don't work)

Update naturalsort_defaultcollator.php. Fixes #13982

Always load authentication apps

This extends Test_NaturalSort to include a basic test for
\OC\NaturalSort_DefaultCollator()

The current code path may trigger situations where the LDAP application is not yet loaded and thus problems with the authentication appeared.

In previous versions of ownCloud the authentication mechanism manually loaded these apps which is why this affects ownCloud 8 and master only for my knowledge. (certainly not 6, maybe 7)

Backport to 8 might be something to consider.

Fixes https://github.com/owncloud/core/issues/14469