Remove duplicated Code (#377)

* Reduce Duplicate Code

* Reduce Duplicate Code

* No Error Logging when "document_root" in Json config is empty

* Update JsonClientConnection.cpp

* Remove obsolete functions

* create readConfig and readSchema function

* set forgotten _error variable

libsrc/utils/jsonschema/QJsonSchemaChecker.cpp

@@ -115,6 +115,7 @@ void QJsonSchemaChecker::validate(const QJsonValue & value, const QJsonObject &s
 		else
 		{
 			// no check function defined for this attribute
+			_error = true;
 			setMessage(std::string("No check function defined for attribute ") + attribute.toStdString());
 			continue;
 		}