Proper rivers between the Great Lakes and Atlantic

[SteelyGlint]

I tried turning the Niagara, St. Lawrence, and Soo Locks into regular rivers, but there were problems
River travel works, but trade posts end up all over the place
Experience shows this is probably caused by lack of proper ocean definition
The Great Lakes area would probably have to be defined as 3 distinct oceans in default.map for this to work fully