Implement handling of prefix values in argument values in extensions independently of YangParserListenerImpl

Currently the config subsystem depends of bended implementation of YangParserListenerImpl where unknown nodes are parsed. If argument in unknown node (Extension statement) contains ":" the argument is evaluated as prefix:value which is incorrect. Config subsystem can't rely on bended implementation and MUST be implemented in way in which configu subsystem itself is parsing arguments of extensions and evaluates parsed values.