[FEATURE] Add config and use composer autoloader.

We use composer already to install SabreDAV. Include config
composer.(json|lock) to install and manage more dependencies
in future.
Also provide PSR-4 autoloading for our namespaced classes, e.g.
"Zotlabs\". To regenerate autoloader maps use:
$ composer install --optimize-autoloader --no-dev

We could also remove the whole vendor/ folder from our repository, but
that would need changes in deployment and how to install hubs and needs
more discussion first.

Zotlabs/Module/Dav.php

@@ -11,9 +11,6 @@ namespace Zotlabs\Module;
 use \Sabre\DAV as SDAV;
 use \Zotlabs\Storage;
 
-// composer autoloader for SabreDAV
-require_once('vendor/autoload.php');
-
 require_once('include/attach.php');
 
 class Dav extends \Zotlabs\Web\Controller {
@@ -74,7 +71,6 @@ class Dav extends \Zotlabs\Web\Controller {
 		$auth->setBrowserPlugin($browser);
 
 		// Experimental QuotaPlugin
-		// require_once('Zotlabs/Storage/QuotaPlugin.php');
 		// $server->addPlugin(new \Zotlabs\Storage\QuotaPlugin($auth));
 
 		// All we need to do now, is to fire up the server