Reallow single quote in file names

Add debug mode back to mailer

`FILTER_SANITIZE_STRING` will still encode everything else.

Only hard depend on the info.xml and not the app.php

Cache \OC\URLGenerator::imagePath

This re-adds the debug mode for the mailer which will log the whole SMTP traffic within the log file if enabled.

Add whitespace to right of list to prevent accidental deletion when scrolling

fix comment

Remove unused section

Add version and path to cache prefix

This section is now unused as the security configuration has to happen on the webserver layer since https://github.com/owncloud/core/pull/14651

Use a closure for the files app entry and deprecate old methods

Prevents to have the cache reused by other instances on the server which have possible the same instance ID and also invalidates older cache entries after an upgrade which can cause unwanted side-effects.

Impact for deployment: The same cache will only get used if ownCloud is installed with the same version and under the same path. But this should be a basic requirement anyways.

\OC\URLGenerator::imagePath is a really expensive operation due to all the I/O handling and can really benefit from caching.

Fix PHPDoc and Co.

Introducing the Raw media types

Issue/14881 closures for navigation entries

Migrate OC_Mail to SwiftMailer

Ref https://github.com/owncloud/core/pull/14929#discussion_r26501240

Fix scanFile signature warnings

Fix setup config namespace

Fix user preference key definition for insertIfNotExists()

Write the parameter 'logtimezone' into config.php during setup

Wait with getting the timezone from the smb server until we need it

This speeds up all pages that don't use the navigation by 0.04sec per app,
because we don't need to create the routing anymore, unless we really need to.

stupid me :(