Replaced vector_owner base class with two vector helper functions impl::remove_duplicates() and impl::equals_unique_vector().
 On branch master
 Changes to be committed:
	modified:   bin/Debug/schoolMarkLogger
	modified:   competence.hpp
	modified:   lesson.hpp
	modified:   main.cpp
	modified:   quartal.hpp
	modified:   school_year.cpp
	modified:   school_year.hpp
	modified:   user.cpp
	modified:   user.hpp
	new file:   vector_helper.hpp
	deleted:    vector_owner.hpp