All property, both real and personal, of a spouse owned or claimed before marriage, and that acquired afterward by gift, devise or descent, shall be the separate property of that spouse; and laws shall be passed more clearly defining the rights of the spouses, in relation to separate and community property; provided that persons about to marry and spouses, without the intention to defraud pre-existing creditors, may by written instrument from time to time partition between themselves all or part of their property, then existing or to be acquired, or exchange between themselves the community interest of one spouse or future spouse in any property for the community interest of the other spouse or future spouse in other community property then existing or to be acquired, whereupon the portion or interest set aside to each spouse shall be and constitute a part of the separate property and estate of such spouse or future spouse; spouses also may from time to time, by written instrument, agree between themselves that the income or property from all or part of the separate property then owned or which thereafter might be acquired by only one of them, shall be the separate property of that spouse; if one spouse makes a gift of property to the other that gift is presumed to include all the income or property which might arise from that gift of property; spouses may agree in writing that all or part of their community property becomes the property of the surviving spouse on the death of a spouse; and spouses may agree in writing that all or part of the separate property owned by either or both of them shall be the spouses’ community property.