BUGFIX: No uppercase characters allowed in node names

The changed generation of node names must avoid uppercase characters.

This is a followup to neos/neos-development-collection#1523

Classes/TYPO3/Neos/Service/NodeNameGenerator.php

@@ -56,7 +56,7 @@ protected function generatePossibleNodeName($idealNodeName = null)
         if ($idealNodeName !== null) {
             $possibleNodeName = \TYPO3\TYPO3CR\Utility::renderValidNodeName($idealNodeName);
         } else {
-            $possibleNodeName = 'node-' . Algorithms::generateRandomString(13);
+            $possibleNodeName = 'node-' . Algorithms::generateRandomString(13, 'abcdefghijklmnopqrstuvwxyz0123456789');
         }
 
         return $possibleNodeName;