This charter may be amended by proposals therefor submitted by the council, or by the mayor upon initiative petition of the people as provided by the state constitution, at a general or special election, ratified by a majority of the qualified electors voting thereon, and approved by the governor as provided by the state constitution. If more than one amendment is proposed, all of them except those which are so interrelated that they should be ratified or rejected together, shall be submitted in such manner that the electors may vote on them separately. A proposition to amend this charter may be either in the form of a proposed amendment to a part or parts of the charter or of a proposed new charter.