[issue/6263] layout.user.php code is not valid markup

Mobile style for public links: files, folders, picture sets

- for supported previews are shown with a size of 500px; icons with a size of 128px

Added error message for when target folder was removed

Add/fix Microsoft Office file icons.

Add white color variant of checkmark icon

Whent trying to upload/rename/create files in a folder that was removed
or rename, the correct error message is now shown.

In the case of upload of multiple files, the upload is cancelled.

This situation can happen if the target folder was renamed or removed
from another browser window or client.

[ocs share api] public upload is also possible with encryption enabled, since OC6

Fix warnings in logs when renaming over the web UI

The determineIcon() method was expecting attributes to be set which
caused warnings about undefined indices in the error log.

This fix pre-initializes the array with 'directory' and
'isPreviewAvailable' to make them disappear.

Sharing fixfiledownloadlink

[ocs share api] use error code 403 if sharing is not permitted

Remove unused $freeSpace

Added exception logger plugin for sabre connector

use localised date in notification mails

remove the form, it isn't needed here

Add 'mail_from_address' configuration

Add check for apc.enabled option

Remove %webroot% from CSS

Whenever an exception occurs in the sabre connector code or code called
by it, it will be logged.

This plugin approach is needed because Sabre already catches exceptions
to return them to the client in the XML response, so they don't appear
logged in the web server log.

This will make it much easier to debug syncing issues.

Cleans up Core apps for relative(em) to absolute(px) styles.

Converts em to px values for styles in Files.

[encryption] update file cache after the file was written

prevent autofill for password change settings, prevent leak of existing password

add expire date to link share if possible