Fix amalgamation for international aviation and navigation fuels

[kaskranenburgQ]

Problem
The international navigation and aviation fuel datapoints use sum for amalgamation. This breaks when aggregating municipalities into provinces/RES-regions.
Right now, we align these values with the national dataset at municipality level (so we can model Schiphol properly). But when you sum up 18 municipalities into a province, you get 18x the national value, which is obviously wrong.

Solutions
Quick fix: Change amalgamation method to average. This stops the multiplication issue.
Proper fix: Map international transport demand to where it actually happens. Schiphol's aviation demand should only be in Haarlemmermeer, not spread across every municipality. Same for navigation and ports.
The proper fix lets us keep sum as the method and gives accurate data, but requires mapping work. Quick fix can be implemented now.

[mabijkerk]

@kaskranenburgQ for the quick fix, applying max or min would work as well right? I think applying the quick fix is quite urgent right, the current demand makes no sense. It should also be quite fast to implement, just change the method, apply amalgamation and export.

[kaskranenburgQ]

@mabijkerk
Yes, Avg, max and min would all work in this case.