Solve import order problem when POULibrary imports ConfigTreeNode because of UserAddressedException. Now UserAddressedException is declared in POULibrary.py, as a quick and dirty fix, but some independant module should be created for beremiz exceptions in general.

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot URI_location="LOCAL://">
  <TargetType/>
  <Libraries Enable_Native_Library="true"/>
</BeremizRoot>