Section XVIII-4(a): (a) Reservation of powers.

  The powers of the initiative and referendum, reserved by this
Constitution to the people of the State and the respective
counties and districts therein, are hereby reserved to the people
of every municipal corporation now existing or which shall
hereafter be created within this State, with reference to all
legislative authority which it may exercise, and amendments to
charters for its own government in accordance with the provisions
of this Constitution.