add releasing of assigned unique id in ZRegistrable destructor
add memory deallocation in ZLogger::Log
add ZServiceManager::Unregister method;
add ZServiceBox's destructor for convenience;
reorganize test fixture classes for ServiceManager's tests
add default copy constructor and assign operator for ZRegistrable
inherit ZMonster from ZRegistrable; forbid manual creation of ZMonster;
add fabric method to create registered ZMonster instances
rename prz::utils namespace to prz::utl