Refactor contains and containsOnlyValue

• contains should be changed to find (c.f. std::find)
• containsOnlyValue should be generalized to have similar interface like std::all_of, std::any_of, std::none_of: https://en.cppreference.com/w/cpp/algorithm/all_any_none_of
• maybe we should add operator== for comparing an array/vector with a scalar/ValueType