Move the setup of external share mounts to a mountprovider

fix possible infinite loop when reading groups in the wizard

Fixes last causes for WSOD

Fix single file download

Remove oc_storages entries after removing ext storages

Mark shares as dirty when changing permissions

When removing external storages, either system-wide or user-wide,
automatically remove the matching oc_storages and oc_filecache entries.

This can only work if the backend configuration doesn't contain any
substitution variable $user in which case the storage id cannot be
computed, so this case is ignored for now.

Propagate shares etag when group membership changed

Path to mount.json needs to be absolute in config.sample.php

Fix importing of certificates

Add \OCP\IRequest::getHttpProtocol

OC_Log not longer exists

Only allow valid HTTP protocols.

Ref https://github.com/owncloud/core/pull/19537#discussion_r41252333 + https://github.com/owncloud/security-tracker/issues/119

Fixes https://github.com/owncloud/core/issues/19601

Reset to auto if not set

Reload the page when an app needs an update after being enabled

Lock zip content

OCS provisioning API more tests

update licence headers via script