[TASK] do not listen to NodeData doctrine events, but to Node Signals
[TASK] fix doc comments
[FEATURE] add "from()" method to QueryBuilderInterface
[TASK] rename IndexingHelper to Indexing in Eel
[TASK] "evaluateEelExpression" works with Node instead of NodeData
[TASK] make extractPropertiesAndFulltext and extractFulltext work as in ElasticSearch
[FEATURE] Error Handling in AbstractNodeIndexer