User/Cleanup

* the great unfuckening of user and displayName
    * `login` is purely used as login with AUTH_MODE_SELF
    * `email` may now also be used to log in (if the system knows it)
    * `username` is purely used for display around the site, and lookups from web context
    * both must exist because of external logins
        a) that may be not unique
        b) you may not want to share with the rest of the world
    * todo: implement rename ( because of b) )

includes/ajaxHandler/edit.class.php

@@ -41,7 +41,7 @@ class AjaxEdit extends AjaxHandler
 
         $targetPath = 'static/uploads/guide/images/';
         $tmpPath    = 'static/uploads/temp/';
-        $tmpFile    = User::$displayName.'-'.Type::GUIDE.'-0-'.Util::createHash(16);
+        $tmpFile    = User::$username.'-'.Type::GUIDE.'-0-'.Util::createHash(16);
 
         $uploader = new \qqFileUploader(['jpg', 'jpeg', 'png'], 10 * 1024 * 1024);
         $result   = $uploader->handleUpload($tmpPath, $tmpFile, true);