The City shall have and may exercise all powers which are now or may hereafter be conferred upon or delegated to cities under the constitution and laws of the Commonwealth and all other powers pertinent to the conduct of a city government the exercise of which is not expressly prohibited by the said constitution and laws and which in the opinion of the council are necessary or desirable to promote the general welfare of the city and the safety, health, peace, good order, comfort, convenience and morals of its inhabitants, as fully and completely as though such powers were specifically enumerated in this charter, and no enumeration of particular powers in this charter shall be held to be exclusive but shall be held to be in addition to this general grant of powers.