No issue - remove dead code

- get rid of file src/plugin/PluginDomTraverser.h because it's pointless
- remove free function `CreateLowProcess` from src\plugin\PluginClass.cpp. It's not used and obsolete.
- get rid of CPluginDomTraverserCacheBase::ShowNotification method, it's not used and the body is pointless

--HG--
extra : amend_source : 1b3a018eaf2e6702ef4c5479dbc77cdd679885e5