NaturalSort performance improvements

prevent creation of ghost directories

Add a controller and reponse for ocs

Cache app versions

drop OC\Preferences

drop OC_Preferences

Respect `mod_unique_id` and refactor `OC_Request::getRequestId`

A combination of using isset() instead of count() or strlen(), caching the
chunkify function, and replacing is_numeric() with some comparisons

Add a better way to check if an avatar exists for the user

no fruitless count attempts, and notification should disappear

Check directory handle before we use it

Avoid dropdown to float under sidebar for mid narrow screens

Clean up files_external

When `mod_unique_id` is enabled the ID generated by it will be used for logging. This allows for correlation of the Apache logs and the ownCloud logs.

Testplan:

- [ ] When `mod_unique_id` is enabled the request ID equals the one generated by `mod_unique_id`.
- [ ] When `mod_unique_id` is not available the request ID is a 20 character long random string
- [ ] The generated Id is stable over the lifespan of one request

Changeset looks a little bit larger since I had to adjust every unit test using the HTTP\Request class for proper DI.

Fixes https://github.com/owncloud/core/issues/13366

Use transactions when renaming directory contents

Disable autocomplete for SMTP Password

external user app: Add note to enable it first

Updated the media type of some font types

Allow application-specific favicons

Streamline CSRF and login check

Do not change color of 'new' button on hover and make new file menu more consistent with button

Use 403 instead of 200 response

Don't encode url unecessary twice

Reduce log level of bind failed to WARN - fixes  #11624

Catch exception properly

Coherent use of "SQLite" in lines 119 and 124

Coherent use of "SQLite" in lines 159 and 161

Revert "adding OC-ETag header"

In line 161, "SQLite" has now the same capitalisation as in line 159.

Just a cosmetic detail, but very obvious when working on localisations.